Adv Higher Unit2

Advanced Higher Biology UNIT 2 Environmental Biology

Introduction to Ecology The study of ecology is a scientific discipline that attempts to understand the interactions between organisms and their environment. This Unit considers the biological processes that result in the flow of energy and circulation of materials in ecosystems. Emphasis is placed on the process of decomposition because of its key role in recycling materials. The interactions within ecosystems are studied by consideration of the abiotic and biotic factors that affect ecosystems. We will also look at the consequences of such interactions as well as human impact on the environment.

(a) CIRCULATION IN ECOSYSTEMS 1. Energy (Energy fixation & Energy flow) 2. Circulation of nutrients (Decomposition, Nutrient Cycling – N & Ph Cycles)

Energy Fixation Photosynthesis is fundamental to energy flow through an ecosystem. It is achieved by the autotrophic organisms that convert the energy of sunlight into chemical energy. Energy fixation is achieved by photosynthesis . All organisms require energy to carry out cellular activity, growth and reproduction. They obtain that energy from the food they eat.

Nutrition AUTOTROPHS The term autotrophic ( 'self-feeding' ) defines organisms which are able to use external sources of energy in the synthesis of their organic food materials. PHOTOAUTOTROPHS : use light energy, via photosynthesis, to make their organic molecules CHEMOAUTOTROPHS : use energy from breakdown of inorganic molecules to synthesis complex organic molecules

HETEROTROPHS Heterotrophic ( 'other-feeding' ) organisms obtain their energy by breaking down substances obtained from the bodies of other organisms. HERBIVORES [= Primary Consumers] : feed only on green plants CARNIVORES [Secondary/tertiary Consumers] : feed only on other animals OMNIVORES : feed on both plants and animals

SAPROTROPHS Saprotropic ( ‘decay-feeding’ ) organisms obtain their nutrients from non-living organic matter, usually dead and decaying plant or animal matter, by absorbing soluble organic compounds. Since saprotrophs cannot make food for themselves, they are considered a type of heterotroph. They include most fungi (the rest being parasites); many bacteria and protozoa; animals such as dung beetles and vultures; and a few unusual plants, including several orchids.

Productivity PRIMARY PRODUCTIVITY : The amount of light energy converted into chemical energy by autotrophs in an ecosystem during a given period of time. Measured by the rate of accumulation of BIOMASS (dry weight of vegetation) in the ecosystem [usually expressed as per unit area in a given time e.g. g/m 2 /yr] GROSS PRIMARY PRODUCTIVITY (GPP): the total primary productivity HOWEVER: Remember that plants not only photosynthesise, they also respire . Therefore not all the material produced is stored (and available as food for the primary consumers). Some of it is used for cellular respiration and other metabolic activities by the plant itself.

Net Primary Productivity The energy available to the next level in a food chain or food web is the gross primary productivity (GPP) minus the energy used by the plant during respiration (R) and is called the NET PRIMARY PRODUCTIVITY (NPP) This can be written as an equation: NPP = GPP - R Net primary productivity (NPP) is of interest because it represents the chemical energy available to the primary consumers (herbivores) and is the beginning of the flow of energy through an ecosystem.

Factors affecting productivity The same as those affecting photosynthesis! Light Intensity Temperature Rainfall Soil Water/Nutrients CO 2 concentration

Energy Flow Energy fixation and productivity are the basis of ecosystem productivity. In this section the aim is to discuss how that energy flows through an ecosystem, and to consider the efficiency of that energy flow.

Ecological Niches There are three basic niches (or feeding relationships) in the flow of energy through an ecosystem: producers (autotrophs) , consumers ( heterotrophs ) and decomposers (saprotrophs) .

Energy in an Ecosystem FLOWS from the SUN to Autotrophs (Producers) then to Heterotrophs (Herbivores) that eat the Autotrophs, then to Heterotrophs (Carnivores) that feed on other organisms.

Trophic Levels Feeding relationships and therefore the flow of energy can be represented as a food chain. Each link in the chain is called a trophic level ( ‘ trophic’ meaning ‘ feeding’ ) Each trophic level is the same number of steps from the Sun: - Producers (Autotrophs) are the 1st Trophic Level - Herbivores are the 2nd Trophic Level - Carnivores are the 3rd/4th/5th Trophic Levels Most Animals (carnivores) feed at more than one Trophic Level In most ecosystems the feeding relationships (and the transfer of energy) are represented more accurately by a food web

Energy Transfer & Efficiency The leaves only use some of the light energy which shines on them for photosynthesis. The rest is … Consider this simple food chain: REFLECTED off the leaves TRANSMITTED through the leaves or belongs to WAVELENGTHS that cannot be used .

Energy Transfer & Loss BUT , only about 1% of the light energy striking a plant is converted into net primary productivity and available to be eaten by the caterpillars. Only a proportion of this energy (that contained in the leaves and shoots) is consumed by the caterpillars, where most of it is used in respiration and heat production, and some is egested as waste . Only a small fraction (about 10% ) is used for growth and available to the next trophic level, the sparrow. Similarly only about 10% of the energy the sparrow receives from the caterpillars is available to be passed on to the next trophic level (the eagle)

Ecological Efficiency The ecological efficiency is the ratio of net productivity (ie the amount of energy) at one trophic level to net productivity at the level below NPP (trophic level x) : NPP (trophic level x -1) Ecological efficiencies vary depending on the organisms involved but usually range from 5-20%. This means that 80-95% of the energy at one level never transfers to the next. Because energy diminishes at each successive trophic level, food webs rarely contain more than 4 or 5 trophic levels. This is the reason why, generally speaking, the biomass of and the number of organisms in each trophic level decrease as you move along a food chain

Pyramids of numbers, biomass and productivity In an ecosystem, productivity , biomass and numbers of organisms tend to DECREASE at each trophic level in a food web. This information can be quantified and illustrated diagramatically as ecological pyramids

Pyramids of Number Numbers of organisms in a given area in a given time are counted and then grouped into trophic levels. Pyramids of numbers typically show a broad base of producers and a successive decrease in number of animals at each level There are several situations that show inverted pyramids of numbers. For example, a tree, as the primary producer, supports large numbers of insects, which in turn are the food source of large numbers of birds or other predators

Pyramids of Biomass Each block = total dry mass of organisms at that trophic level. At each level the biomass decreases . Normally a pyramid of biomass would have a broad base, getting narrower at each succeeding level. Occasionally, however, inverted pyramids of biomass can be found where the primary consumers outweigh the primary producers. E.g. In aquatic ecosystems the primary producers are algae. They are very productive and have a high turnover rate . This means that they grow in numbers rapidly but are also eaten in large numbers by zooplankton and small fish. Thus at any given time the biomass of the producers will be less than that of the primary consumers.

Pyramid of Productivity Size of each block is proportional to the productivity of (or energy available at) each level. The producers form the foundation of the pyramid Qu: Look at the inverted pyramid of mass found in a marine phytoplankton food chain. Would the pyramid of productivity for this food chain be inverted or upright?

Circulation of Nutrients Despite an inexhaustible influx of energy in the form of sunlight, continuation of life depends on recycling of essential chemical elements. These elements are continually cycled between the environment and living organisms as nutrients are absorbed and wastes released. The cycling of nutrients from the decomposition of dead or decaying matter , provides essential elements required for metabolic processes, such as photosynthesis, and constructing fundamental organic molecules, such as amino acids and nucleic acids.

The role of soil in decomposition Soil consists of 2 main components… INORGANIC ORGANIC Oxygen and moisture , trapped in the spaces (pores) between the soil particles, are required by micro-organisms to decompose materials. Dead/Decaying organisms, parts of organisms, faeces and urine derived from weathering of rocks. Type determined by relative proportions of SAND , SILT and CLAY particles very important agriculturally.

The structure of soil The structure of soil is vital to nutrient recycling in terrestrial ecosystems Organic litter : plant/animal debris Topsoil containing humus : roots, invertebrates, micro-organisms Leaching of nutrients from the soil Subsoil : rich in minerals & organic material, some roots Weathered rock : sand, gravel, clay Impermeable Bedrock

Soil fauna Wide variety including … FUNGI BACTERIA - [Insert Soil micro-organisms table] INVERTEBRATES - worms, woodlice, spiders, nematodes, larvae Essential to soil productivity - directly affect quality of soil

Rhizosphere The area where plant roots and soil come into contact. There are large numbers of micro-organisms here that differ in species composition. The major micro-organisms found are the bacteria whose growth is stimulated by various nutrients released by the plant roots. In exchange, the by-products of microbial metabolism that are released into the soil stimulate plant growth.

Decomposers and Detritivores These organisms feed on waste or dead organic matter such as dead leaves, dead bodies, or waste products, decomposing it by producing enzymes to break it down. Action of detritivores increases the activity of decomposers :- DETRITIVORES : Detritus eating soil invertebrates e.g. Earthworms, woodlice, spiders and nematodes . Physically reduce detritus particle sizes to produce humus [ FRAGMENTATION = Larger surface area for decomposers to work on!] Enhance fertility of the soil by incorporating leaf surface litter into the soil PHYSICAL DECOMPOSITION DECOMPOSERS : Fungi & Bacteria Use waste materials as energy, carbon & nutrient sources Carry out respiration to release CO 2 Chemically breakdown [using ENZYMES ] detritus (decaying matter) to release inorganic ions ( mineralisation ) CHEMICAL DECOMPOSITION

Detritus Food Chain A food chain based on dead organic material A food chain containing a primary producer which is a soil invertebrate e.g. Earthworm. A Detritus food chain is essential to the energy flow of an ecosystem.

Decomposition The breakdown of dead organic matter(involving both physical and biological processes) with the release of inorganic nutrients into the soil. These nutrients are then available for uptake by plants and other primary producers Undecomposed material = LITTER [DETRITUS] Completely decomposed matter = HUMUS

Humus Completely decomposed material Dark brown in colour Composition varies depending on which organic molecules are present Improves aeration, water and nutrient retention; and so soil structure  Humus content =  soil fertility

Mineralisation Occurs at the same time as humus is being formed Process which changes essential minerals e.g. N , P and S from Organic  Inorganic compounds e.g. ammonium , orthophosphate and sulphate Results in nutrients and minerals being released from dead organisms into a food chain

Rate Of Decomposition This varies within different biomes and is dependent on several factors: Type of organic matter Number and types of decomposers and detritivores Environmental conditions i.e. temp, moisture etc

The Carbon Cycle Carbon is removed from the atmosphere by fixation during photosynthesis and returned by respiration, decomposition & burning fossil fuels

The Nitrogen Cycle 1) FIXATION : the reduction of atmospheric nitrogen to ammonia by CYANOBACTERIA . Rhizobium fix nitrogen in the root nodules of legumes. Catalysed by enzyme complex NITROGENASE . LEGHAEMOGLOBIN is a molecule made by both the plant and the bacteria which limits the amount of O 2 reaching the bacteria. This is important as nitrogen-fixing is an anaerobic process 2) NITRIFICATION : the conversion of ammonium to nitrite to nitrates by NITROSOMONAS and NITROBACTER. Nitrates and ammonium are assimilated by plants into proteins and amino acids. They are lost by leaching and denitrifying bacteria. Aerobic process. 3) DENITRIFICATION : returns nitrogen to the atmosphere 4) AMMONIFICATION : the decomposition of organic nitrogen to ammonia Water saturation of the soil affects the cycling of nitrogen. i.e.  H 2 0 =  O 2 anaerobic/aerobic affect different stages of cycle

The Phosphorus Cycle Phosphorus is a major element of ATP, Nucleic Acids, Phospholipids 1) PHOSPHATE added to the soil by the weathering of rocks 2) Taken up by primary producers incorparated into molecules 3) PHOSPHORUS is taken up by consumers 4) PHOSPHORUS returned to the soil by decomposition (faeces/detritus) Phosphate is a limiting factor in the productivity of aquatic ecosystems as it has LOW SOLUBILITY (needed by ALGAE!) Phosphate enrichment can lead to eutrophication (as can excess Nitrogen ) 1 2 3 4

(b) INTERACTIONS IN ECOSYSTEMS 1. Biotic Interactions (Predation, Grazing, Competition) 2. Symbiotic Relationships (Parasitism, Commensalism, Mutualism) 3. Costs,Benefits & Consequences of these interactions (Interactions between species, Interactions with the environment)

Biotic Interactions This is the interaction between living things Predator/prey relationships Plant/herbivore relationships Competition Symbiosis

Abiotic Interactions These are interactions that exist between the organisms and the environment : - Temperature - Light - Pressure - Salinity - Water availability - pH - Nutrients - Exposure to wind or waves

Density Independent Factors These are factors which reduce the population numbers independently of the population density The proportion that dies could be the same whether the population is dense or not - Forest Fire - Floods - Volcanic eruptions - Prolonged drought - Acid rain

Density Dependent Factors These are all biotic interactions These cause the population to decrease when the population is high and increase when the population is low - Predation - Competition - Disease

Inter-specific and Intra-specific Interactions These interactions are always involved in competition INTER is competition between species e.g. GRAZING, PREDATION AND PARASITISM INTRA is competition within the species e.g. TERRITORIAL BEHAVIOUR, DOMINANCE, MATING, RESOURCES

Predation In a predator/prey relationship both the species can benefit Predators obtains food Reduced numbers in prey means more resources for those individuals that are left Both the predator and prey population is governed by one another, however the exact nature of this can differ

Predator-Prey Relationship The pattern between the two can be grouped into 4 types: 1) Stable coexistence : where both populations remain stable 2) Cyclical variations : regular increases and decreases occur in the populations 3) Erratic swings : large scale “blooms” can take place at an irregular time, due to unstable populations of prey or predator, where a small change in the environment can have a major effect on the animal. 4) Extinction : due to over hunting of prey

Predator-Prey Relationship One of these 4 patterns will occur depending on a variety of factors: The CARRYING CAPACITY of the habitat (the maximum number of individuals that can be supported by a particular ecosystem on a long term basis) The PREY REPRODUCTION RATE The PREDATOR REPRODUCTION RATE The degree of FLEXIBILITY of the predator in it’s ability to respond to changes in the prey population

Flexibility of the Predator If the prey increased, the predator would naturally eat more , but this only happens if the predator is not eating it’s maximum number of prey If the increase in prey is long term, then there will be an increase in the predator offspring that survive from reproduction as there is more food available and therefore less competition for food

If the prey population becomes very large there are two possible fates of interaction: STABLE COEXISTENCE : Predators prevent prey from exceeding the carrying capacity To do this predators must reproduce quickly compared to prey and to eat more when there are more prey CYCLICAL VARIATIONS : Here the predators are less responsive to fluctuations, due to slow reproductive rate or have reached a maximum level of feeding

Cycling Cycling results due to time lags, which are the responses of the predator to the change in population numbers of the prey. The prey increases, then in some time the predator population increases As the predator population rises their prey population begins fall The lack of food reduces predator number …………… and so on!

Case Study: Snowshoe Hare and the Canadian Lynx The information on the populations of both animals appears to give the perfect predator/prey relationship in a cycling effect However, there are many other factors to consider, proving only that an ecosystem is a complicated network of interactions

The Role of Predators in Maintaining Diversity in Ecosystems When different species are competing for the same resources, one will succeed at the expense of another The weaker species will be lost from the habitat [COMPETITIVE EXCLUSION] If, however, predation reduces the numbers of strong competing species, the weaker species have more of a survival chance This increases the DIVERSITY OF THE ECOSYSTEM . The more diverse an ecosystem the more stable it becomes, i.e. tends towards a climax community

Defences against predation During the process of evolution, predators have evolved ways to make them more successful at catching their prey ( e.g. claws, fangs, poisons). Similarly, prey organisms have evolved adaptations to help them avoid being caught or eaten by predators

Prey Defences 3 main adaptations: Camoflage - Crypsis - Disruptive colouration Warning Colouration Mimicry

Camoflage An adaptation in form , pattern , colour or behaviour which enables the animal to escape detection by predators by blending in with it’s surroundings Two interrelated but logically distinct mechanisms for this are: CRYPSIS : the ability of an organism to ‘blend in’ with it’s environment DISRUPTIVE COLOURATION : allows an otherwise visible organism to remain indiscernible from the surrounding environment by ‘breaking up’ it’s outline

Cryptic Colouration Blend into the background ! The animal's colours are a random sample of the background Examples: peppered moths, chameleons

Disruptive Coloration Disruptive patterns (spots/stripes/markings) break up an animal's outline Forming a pattern that does not coincide with the contour and outline of the body makes it difficult for other animals to see it!

Warning or Aposematic Coloration This is a form of coloration which discourages a predator from eating an organism There is often a sting, poison, or painful bite associated to it. Animals learn these colours by trial and error

Red, black and yellow are common colours and are called aposematic colours (meaning ‘away signal’) Many individual share the same pattern [ convergent evolution ] This prevents young from having to try many combinations to learn all of the animals not to eat This convergent evolution is a form of mimicry

Batesian mimicry Involves a palatable, unprotected species (the mimic) that closely resembles a dangerous, poisonous or protected species (the model) and therefore is similarly avoided by predators The scarlet king snake on the left is the mimic, and the coral snake on the right is the poisonous one SCARLET KING SNAKE CORAL SNAKE "Red on yellow, kill a fellow. Red on black, won't hurt Jack."

Mullerian mimicry Involves two unpalatable species that are mimics of each other with conspicuous warning coloration (aposematic coloration)

Grazing Grazing is a form of INTERSPECIFIC INTERACTION A ‘GRAZER’ = any species that moves from one ‘victim’ to another feeding on part of it without actually killing it outright e.g. grasshoppers that jump from plant to plant, chewing a portion of the leaves as they go Grazers, like predators, can both INCREASE or DECREASE species diversity depending on the intensity of the feeding of the grazers and on the type of plant being grazed

As an ecosystem tends toward a climax community, the process can be stopped or diverted away from the natural succession This can be unnatural by implementing agriculture OR naturally by grazing animals Grazing animals favour grasses as these species are more vigorous competitors due to low growing points Shrubs have meristems at the tips of shoots, which are easily eaten by grazers

Apical and Basal Meristems Meristem = point of growth in a plant Grasses have BASAL MERISTEMS (growing points under the soil) Shrubs have APICAL MERISTEMS (growing points at the tips of shoots), which are easily eaten by grazers

Overgrazing When overgrazing occurs, this prevents the build up of leaf litter Leaf litter is important in starting bush fires by lightning. Bush fires remove the shrubs from the ecosystem, but grasses thrive as they have basal meristems Therefore if an grassland is overgrazed, shrubs will become more dominant, thus again reducing diversity Many shrubs are not palatable to grazers, therefore they move away from the habitat

Grassland Habitats These habitats provide an area of land which has a huge diversity of organisms living in it If you remove a grazing animal, e.g. rabbits in Britain, the whole diversity soon disappears as the area becomes a wooded community Woods lack diversity of plants, which in turn effects animal diversity, thus species can be lost from the ecosystem Woodland areas have a different soil type which is permanently changed after a wood has been there

Competition Competition is where 2 or more organisms need the same resource , and the resource is limited This does not always result in fighting or confrontation ! Where there is competition, one or both of the organisms will lack the resource When the resource is required by different species, and there is a lack of the resource, then the two organism’s niche overlaps If the resource is unlimited then the overlapping of their niche is not a problem. The GREATER the overlap in the niche the MORE CHANCE there is for competition

Interspecific vs Intraspecific competition INTERSPECIFIC competition is competition between organisms of two different species INTRASPECIFIC competition is competition between organisms of the same species Interspecific competition is not as intense as intraspecific competition, due to organisms of the same species having the greatest overlap in niches

Exploitation and Interference Competition All competitions between organisms can be grouped as EXPLOITATION or INTERFERENCE competition EXPLOITATION is when all individuals have the equal access to the resource, but they differ in how fast or how efficiently they can exploit it INTERFERENCE is when certain individuals are able to restrict or prevent access of others to the resource and so control the use of it

Exploitation Competition There are two possible outcomes from this competition: They will co-exist One of the two will be excluded In theory, if there is enough overlap in their requirements, one species will always have a slight advantage and will succeed at the expense of the other

Gause’s experiment with Paramecium The two species of Paramecium used by Gause grew well by themselves but P. caudium was out competed by P. aurelia when the two were grown together

Interference Competition In this case on organism will often show AGGRESSION to prevent another organism sharing a resource, e.g. territorial behaviour of the robin. The territory contains just enough resources for the breeding pair In plants, this can be seen in the ability for some to GROW QUICKLY and block the sunlight out for others e.g. by growing in a lateral manner

Fundamental Niche and Realised Niche The FUNDAMENTAL NICHE is the theoretical niche containing all of the required resources for an idealistic life This cannot exist as there a huge network of interactions with other species, and each species will try and exploit the resources The actual resources which a population uses are its REALISED NICHE

Case Study of Barnacle populations Semibalanus balanoides Habitat – low tide mark to the lowest high tide mark as they have little toleration to desiccation Chthamalus stellatus Habitat – found in areas of rocks which may be exposed to air for long periods, as they can survive some period of desiccation

Resource Partitioning Species that share the same habitat and have similar needs frequently use resources in somewhat different ways - so that they do not come into direct competition for at least part of the limiting resource This is called RESOURCE PARTITIONING

The Competitive Exclusion Principle Early in the twentieth century, two mathematical biologists, A.J.Lotka and V. Volterra developed a model of population growth to predict the outcome of competition Their models suggest that two species cannot compete for the same limiting resource for long. Even a minute reproductive advantage leads to the replacement of one species by the other

The Damaging Effects of Exotic Species The Rhododendron ponticum is a shrub which was introduced to Scotland It is successful competitor in acidic soils, many soils in the Scottish Highlands are acidic It creates a dense canopy of leaves, which shades smaller shrubs, and therefore is a good INTERFERING competitor In its native habitat it has grazers as they have evolved together, however in Scotland the sheep and rabbits do not eat it

These invasive, non-native species are a major threat to the environment because they ... can change an entire habitat, placing ecosystems at risk crowd out or replace native species that are beneficial to a habitat damage human enterprise, such as fisheries, costing the economy millions of dollars Other examples: The zebra mussel, accidentally brought to the United States from southern Russia, transforms aquatic habitats by filtering prodigious amounts of water (thereby lowering densities of planktonic organisms) and settling in dense masses over vast areas. At least thirty freshwater mussel species are threatened with extinction by the zebra mussel [HANDOUT / RESEARCH]

The Importance of Survival for Weak Competitors Species diversity is important to all ecosystems The diversity provides flexibility when the environment changes Therefore competitors change when the environment changes A less competitive species survives as they can adapt its niche slightly, and therefore maintain a presence They are a valuable reserve for an alternative ecosystem. Without an alternative, if the environment were to change then the stability of the environment would be in jeopardy

Symbiotic Relationships - Parasitism - Commensalism - Mutualism SYMBIOSIS refers to relationships between organisms of DIFFERENT species that show an intimate association with each other Symbiotic relationships provide at least ONE of the participating species with a nutritional advantage 3 types of symbiosis have been recognised depending on the nature of the relationship:

Parasitism Interaction in which one organism, the parasite , derives nourishment from the other organism, the host Parasites are therefore chemoautotrophs This relationship is detrimental to the host, however a true parasite does normally not kill its host

Obligate vs Facultative Most parasites are OBLIGATE - that is they must live parasitically and die when their host dies Obligate parasites also have very few specialised structures for feeding or locomotion Some fungi are FACULTATIVE parasites since they can continue to feed saprophytically once their host has died Fewer facultative parasites have evolved as they must form complicated systems to detect, take in and digest food. Due to natural selection they would be at a disadvantage to obligate parasites.

Parasite Types ECTOPARASITES - remain external to the host e.g. ticks, fleas, leeches ENDOPARASITES - live inside the body of the host e.g. liver flukes, tapeworms, malarial parasites

MICROPARASITES They are small and have a short generation time e.g. viruses, bacteria and protozoans [ Plasmodium spp ] The duration of infection is short compared to the life span of the host

MACROPARASITES Longer generation time and tendency to persist causing continual reinfection e.g. roundworms tapeworms and fungi Intermediate hosts more common

Parasite Transmission Many parasites complete their entire lifecycle on or in a single host organism However, many alternate between 2 or more host species, specialising on a different host species at each stage in their lifecycle 2 general types of transmission: VERTICAL : from mother  offspring e.g. HIV HORIZONTAL : between members of a population Direct Contact e.g. Headlice Resistant Stages e.g. Liver fluke Secondary host species / Vectors e.g. Mosquitoes

Parasite Transmission Case Study: MALARIA Malaria is a mosquito-borne disease caused by a parasite Plasmodium falciparum , P. vivax , P. ovale and P. malariae People with malaria often experience fever, chills, and flu-like illness Left untreated, they may develop severe complications and die Almost 85% of the world's malaria occurs in sub-Saharan Africa Each year 350-500 million cases of malaria occur worldwide, and over one million people die, most of them young children in sub-Saharan Africa

Humans are the INTERMEDIATE HOST and RESERVOIR of the parasite, and the mosquito is the DEFINITIVE HOST and VECTOR . Female anopheline mosquitoes become infected only if they take a blood meal from a person whose blood contains mature male and female stages of the parasite. A cycle of development and multiplication then begins with union of the male and female gametocytes in the stomach of the mosquito and ends with parasites, called sporozoites, in its salivary glands, which are infective to humans. The time required for the complete maturation of the parasite in the mosquito varies and depends on the Plasmodium species and external temperature. Lifecycle of Malaria Parasite 1 2 3

The gametocytes are ingested by the female mosquito in a bloodmeal from an infected human. The gametocytes fuse to produce a zygote.The zygote secrete a cyst containing sporozoites formed from meiotic divisions

Sporozites enters the liver cell and during the next two weeks the intracellular parasite reproduces by mitosis within a liver cell to form as many as 200,000 merozoites! On maturation, the merozoites rupture the liver cells and are are released into the blood where they invade human red blood cells

In the red blood cells, the parasite matures asexually to produce another 10-20 merozoites which in turn can rupture the red blood cell and invade more liver cells or red blood cells

Evolution of Host/Parasite relationship Most parasitic relationships are very specific and complex The parasite and the host have co-evolved This means that the host has developed a defence mechanism e.g. immune system or hydrochloric acid in the stomach , to prevent the parasite from causing any harm if it has entered the body. The longer the relationship has existed, the more host specific the parasite becomes

Modification of Parasites STRUCTURAL - Absence/degeneration of feeding and locomotory organs - Highly specialised mouth parts as in fluid feeders e.g. aphids - Boring devices to aid entry into host - Attachment organs e.g. hooks or suckers - Resistant outer covering - Degeneracy of sense organs associated with the constancy of the parasites environment PHYSIOLOGICAL - Exoenzyme production to digest host tissue external to parasite - Anticoagulants - Chemosensitivty to reach optimum location in hosts body - Production of anti-enzymes - Ability to respire in anaerobic conditions REPRODUCTIVE - Hermaphrodites - Enormous numbers of reproductive bodies cysts and spores - Resistant reproduction bodies when external to the host - Use of secondary hosts as vectors

Host Responses to Parasite Infection Organisms respond to parasites in different ways: Vertebrate hosts infected with microparasites mount an immunological response Vertebrate hosts infected with ectoparasites have other behavioural strategies e.g. Preening or grooming each other to remove ectoparasites e.g. chimpanzees. Move away from the infected area e.g. caribou move to higher altitudes during the summer months when the mosquito population is particularly dense to avoid attacks Plants respond to parasitic infection in several ways: e.g. in tobacco plants, if just one leaf is infected with the tobacco mosaic virus, there is an increase in the defensive chemicals throughout the plant-protects the plant from a variety of parasites and from the effects of grazing by herbivores. In addition, the plant will often kill the cells in the area that has been infected by the parasite, causing localised cell death. This deprives the parasite of its source of food and prevents parasitic spread to other cells.

Some particularly nasty parasites ... Leucochloridium paradoxum A parasite for sore eyes! Cymothoa exigua Biting Your Tongue, So You Don’t Have To! Sacculina carcini: Reasons You Shouldn’t Pick up a Hitchhiker Screw worms: Causing Trouble Right out of the Hatch

Koch’s Postulates There may be several different organisms growing in an infected sample, although most will have appeared after the initial disease has weakened the host. Koch's postulates need to be satisfied in order to identify the organism that is causing a disease Koch was one of the original researchers into tuberculosis, in the 19th century. In an attempt to define what an infectious disease actually is, he formulated his famous postulates, which now bears his name. Basically if, 1. An organism can be isolated from a host suffering from the disease AND 2. The organism can be cultured in the laboratory AND 3. The organism causes the same disease when introduced into another host AND 4. The organism can be re-isolated from that host THEN The organism is the cause of the disease and the disease is an infectious disease

Commensalism An interaction between species where neither species is dependent on the other for its existence, but in this case only ONE of the partners benefits from the association In the strictest truth very few of these relationships exist, as it is very unlikely the two organisms can live together without them affecting each other Most examples of commensalism relationships are feeding or protection

Commensalism : An Example PORCELAIN ANEMONE CRABS AND THEIR HOST ANEMONES - These crabs are primarily suspension-feeding animals, and they use their large basket-like feeding appendages to sweep the water to get their food - They don't harm the anemones, but they benefit by gaining protection from their host. Few fish will hazard getting eaten by an anemone simply for the chance to snack on the crab

Mutualism An interspecific interaction that benefits BOTH species They exchange food or provide shelter or protection, but may still be able to live an independent life In return for shelter, the clownfish cleans the anemones, chasing away their predators and dropping scraps of food for the anemone to eat

Mutualism: examples There are many different examples of mutualistic relationships: Plants and microbes e.g. rhizobium in root nodules Protists and fungi e.g. lichen Terrestrial plants and insects, e.g. pollination Animals and protists/bacteria e.g. ruminants, corals Animals and other animals e.g. crocodile and plover bird

All orchids depend on fungi called mycorrhizae at some point during their life cycle The fungi grow partly on the root and aid the plant in the uptake of nutrients The fungi benefit as they ingest some of the food from plant photosynthesis

Most plants have to search through the soil with their roots to find nitrogen which is a critical nutrient required for growth Legumes, however, form symbiotic relationships with Rhizobium bacteria The Rhizobium live in little nodules in the roots of the legumes and fix atmospheric nitrogen into ammonium or nitrate, forms of nitrogen that can be used by the plant i.e. Rhizobium turn air into fertiliser! The plant benefits because it gains nitrogen. The bacteria benefit because they get sugars and nutrients to survive

The Costs, Benefits and Consequences of Interactions - Interaction between species - Interactions with the environment We have studied various types of biotic interaction that exist between species in an ecosystem. Now we are going to look at these interactions again, but this time we are going to concentrate on the COSTS , BENEFITS and CONSEQUENCES that these interactions have to the different species

Interactions between species: SUMMARY

Effects of Host Health and Environmental Factors In most symbiotic relationships, a STABLE relationship exists between the two species involved This is perhaps most important in parasitic relationships where it is necessary that the host, although affected in a negative way by the relationship, nevertheless remains healthy enough to be able to tolerate the parasite without being affected too seriously. If it is, it may die, which would be detrimental both to the host and to the parasite

However, this stable balance in a parasite/host relationship can be changed by either: Health and development of the host ( BIOTIC factor) or Environmental conditions ( ABIOTIC factors) These factors are crucial in altering the balance of an ecosystem In general if the health of the organism is good then it will hardly feel the effects of some of the environmental factors such as cold and wet conditions However if an organism is weak, then these factors will be detrimental e.g. HIV infection, overcrowding in seedlings, Botyritis infection in raspberries

Examples People who are HIV positive and whose immune system is therefore compromised, tend to be more at risk from opportunistic infections like pneumonia and tuberculosis than individuals whose immune system is healthy Seedlings which are grown in overcrowded conditions tend to grow spindly and weak and are more at risk of infections (which can pass more quickly from one individual to another in overcrowded conditions) than ones given more space. This is why gardeners 'thin' their crops of seedling plants, so that those which remain will have a better chance of growing into healthy adult plants, producing more, larger blooms etc . Soft fruits such as raspberries are prone to a parasitic fungal infection called Botrytis . However, how badly the fruit is affected by the parasite is dependent in part by how humid the environment is

The management of symbiotic relationships THEREFORE , host health and environmental conditions, such as overcrowding and humidity, can alter the balance of host/parasite interactions Humans can MANAGE these factors to change the balance in favour of the host species in a variety of ways: by improving the quality of the host environment ( e.g. reducing overcrowding) and by using DRUGS , PESTICIDES and HERBICIDES .

Drugs An example of the use of drugs to alter the balance in the hosts favour is the use of anti-fungal ointment and powder in the treatment of athlete's foot - a common fungal infection in humans Also many farmers regularly include antibiotics in their animals' feed to prevent infection and so speed up the rate of growth of the animals. This activity is controversial, however, as it may be partly responsible for the evolution of antibiotic resistant bacteria

Pesticides Pesticides are chemicals used by farmers to kill insects and other animals which feed on or otherwise adversely affect crops and reduce the size of the crop yield

Herbicides Herbicides are chemicals used by farmers to kill other plant species which compete with the crop plants for resources such as space, light and water Such competition again, would reduce the growth of the crop plants and therefore also reduce the yield In order to prevent the crop plants being harmed by herbicides, selective herbicides are use These target specific types of plant - there are some which affect broad-leaved plants while leaving narrow-leaved plants unaffected while others do the opposite

Interactions with the environment The Change of the Natural World An organisms interaction with its environment can change very quickly: e.g. rain, wind, sunlight, cloud cover Or more slowly on a monthly basis: e.g. seasons Longer timescales – continental drift and other geological effects, ice ages etc. All organisms within their lifespan have evolved ways to adjust to these changes However, changes can cause stress to the organism, where the condition is outside of their normal physiological range

Despite changes in their external environment, organisms must maintain a constant internal environment : HOMEOSTASIS Therefore, organisms must adapt to maintain a constant internal environment, or become restricted within a very small habitat Organisms have evolved a variety of BEHAVIOURAL and PHYSIOLOGICAL mechanisms to enable them to maintain homeostasis and deal with these changes : BEHAVIOURAL PHYSIOLOGICAL AVOIDANCE REGULATION & ADAPTATION TOLERANCE & RESISTANCE

Behavioural Responses - AVOIDANCE Changes in an organism's behaviour which can be observed and which help them to survive changes in their environment desert mammals being nocturnal and living in underground burrows during the day to escape the heat of the desert sun Hibernation or migration to avoid low temperatures in winter e.g. swallows, whales, wildebeest Deciduous trees lose leaves in the low light intensity periods Sheep huddle in cold conditions Some animals adjust themselves to a particular position e.g. bees use wings to cool the hive All avoidance usually involves a considerable investment of energy from the individuals concerned, but is beneficial in the long-term

Physiological Responses Changes in the way an organism's body functions to enable it to survive in changing circumstances Many of these responses enable an organism to show a certain tolerance to the changes in its environment Examples: The camel's body tissues are very tolerant to dehydration - it can lose up to 30% of its body water and still survive. In humans a 10% water loss causes kidney failure We shiver, hairs stand up, go pale etc in response to cold Wilting in plants Growing a thick coat of fur

Information on a physical response to an environmental change can be turned into a RESPONSE CURVE This allows you to identify the optimum conditions and the range in which the organism will survive Response curves vary with SPECIES , STAGE OF LIFE and HEALTH of organism when exposed to the stress It also varies with the TYPE and INTENSITY of the stressful situation

Response curve Although organisms can tolerate a range of external environmental changes, they function most efficiently at certain optimum environmental conditions. An organism's responses to a changing environmental factor can be studied in the laboratory and a tolerance, or performance, curve can be produced

Adaptations in Plants There are two types of plant that have adapted to controlling water concentrations in different habitats XEROPHYTES HYDROPHYTES Xerophytes are adapted to habitats where transpiration rates are high. These could be hot dry habitats which lack soil water (desert) or exposed windy habitats (moorland) Hydrophytes are adapted to living in submerged or partly submerged conditions in aquatic habitats

XEROPHYTES Sunken stomatal pits Succulent tissues Leaf reduced to spines Long roots Stem with rounded shape Reversed stomatal rhythm Thick, waxy cuticle Rolled leaves Hairs

HYDROPHYTES Aquatic plants have a problem of obtaining oxygen The hydrophyte overcomes this problem by having air filled cavities Oxygen formed in photosynthesis is held within these air spaces Reduction of xylem is a further adaptation Water provides support for the plant, therefore the use of xylem in support is not required Any xylem found is located in a central column for maximum flexibility

Homeostasis Process of maintaining constant internal environment Maintains INTRA cellular and EXTRA cellular fluids at a relatively constant ionic and osmotic compositions despite fluctuations in external conditions Abiotic factors e.g. water, light, temp., soil nutrients etc largely determine what organisms live there, homeostasis has enabled organisms to inhabit a diverse range of environments and to exist within narrow physiochemical ranges When this external environment CHANGES there are 2 basic patterns of response: CONFORMATION : change in internal environment with the external environment REGULATION : maintenance of internal environment regardless of changes in the external environment

Conformation Where internal variables fluctuate DIRECTLY with the external environment Survival depends on the cellular resistance to damage Osmoconformers : Marine invertebrates, such as crabs, shrimp and jellyfish .They are isosmotic and their body fluids are isotonic with their environment (conc. of solutes in the extracellular fluids is equal to that of the surrounding seawater). Therefore, no osmotic gradient exists, so no water enters or leaves the body of the organism. Osmoconformers do not alter their internal solute concentration Poikilotherms : Animals whose body temperature varies with the surrounding environment. These are usually ectotherms (cold-blooded) that absorb heat from the surrounding environment e.g. snakes, lizards and marine fish

Regulation Where the internal variables are maintained at levels DIFFERENT from their environment. This requires significant ENERGY COST Osmoregulators : e.g. freshwater organisms, terrestrial animals, body fluids are not isotonic with the environment and so need to use energy to regulate their internal osmolarity by excreting excess water or taking in additional water.They use a variety of osmoregulatory mechanisms to do this. In hypotonic environments : they GAIN water by osmosis In hypertonic environments : they LOSE water by osmosis Homeotherms : are animals that maintain a constant body temperature. These are usually endotherms (warm-blooded) that derive heat from metabolism e .g. mammals, insects, birds

Habitat occupation of conformers & regulators CONFORMERS can only survive in habitats which provide their particular environmental conditions, although they conserve energy by not regulating REGULATORS use a lot of energy to carry out their homeostatic activities. However, the huge advantage they have is that they can colonise a range of different habitats since they can maintain their internal environment - thus can exploit habitats which conformers cannot!

Dormancy Period in the life of an organism during which the metabolic activity is greatly reduced This allows the organism to survive: Bad environmental conditions Severe resource shortage It can also allow for dispersal or internal change

Predictive vs Consequential 2 types of dormancy exist: PREDICTIVE : occurs in advance of adverse conditions e.g. hibernation CONSEQUENTIAL : occurs in response to prevailing conditions e.g. seed dormancy due to draught

Dormancy forms RESTING SPORES : found in a wide diversity of forms. Temperature and draught resistant stages exist in bacteria, fungi, plants and lower animals HIBERNATION – a period of inactivity in mammals associated with animals physiological changes resulting in a lowering of metabolic rate to conserve energy during periods of environmental extremes e.g. polar bear, dormice AESTIVATION – a period of inactivity associated with hot, dry periods [usually summer] during which the organism remains in a state of torpor with reduced metabolic rate e.g. lung fish DIAPAUSE – a form of dormancy typically found at a specific stage in an insect life history and involving complete cessation of growth and development together with suspended metabolism. This is controlled by hormones

AESTIVATION : Example African and South American lungfish are capable of surviving seasonal desiccation of habitats by burrowing into mud and aestivating throughout the dry season Changes in physiology allow the lungfish to slow its metabolism to greater than 1/60th of the normal metabolic rate, and protein waste is converted from ammonia, to less-toxic urea, (normally, lungfish excrete nitrogenous waste as ammonia directly into the water)

(c) HUMAN IMPACT ON THE ENVIRONMENT Changes to Ecosystems (Changes in complexity, Effects of Intensive Food Production, Effects of Increased Energy Production, Pollution)

Changes in Ecosystem Complexity Communities are always changing, usually from simple to more complex in a process called ECOLOGICAL SUCCESSION Succession is not affected by seasons and is the relatively orderly and repeatable series of changes in the types of species which occupy a given area through time It often begins with unstable, immature communities (pioneering, opportunistic, r-strategists) and proceeds to more mature, stable communities dominated by K-strategists

Types of Succession ALLOGENIC SUCCESSION: species composition is disturbed by environmental factors unrelated to the organisms present e.g. Hurricanes, forest fires, flooding, climate changes AUTOGENIC SUCCESSION : the changes in environmental conditions which leads to changes in species composition in an ecosystem are caused by the biological processes of the organisms themselves e.g. trees shading and killing plants underneath that require high sunlight [Includes Primary & Secondary Succession]

Allogenic Succession Serial replacement of species, driven by changing external geophysical processes Examples: silt deposition in a pond, changing it from an aquatic to a terrestrial habitat increasing salinity of a sea climate change

Autogenic Succession Change of species driven by biological processes changing conditions and/or resources Examples: organisms living, then dying, on bare rock trees shading and killing plants underneath that require high sunlight

Primary Succession Primary Succession : Occurs on barren habitats e.g. rock, sand, clay, ice this means that there is NO SOIL present Pioneering organisms colonise and modify the environment until new niches occur Slow process - may take thousands of years Time Unstable PIONEER Community [lichens, mosses] Stable CLIMAX Community [Trees]

Secondary Succession Secondary Succession : Occurs where an existing community has been cleared by some disturbance. TOP SOIL PRESENT Disturbance can be either natural e.g. forest fire, hurricane or man-made e.g. deforestation, agriculture Faster than primary succession Pioneer communities tend to be annual plants Time

In 1850, Connecticut was almost entirely open land cleared for farming or timber. Today, Connecticut has been mostly reforested through the process of secondary succession as farming has left the state since the 1800's This area has not been cleared in over fifty years. These trees represent the CLIMAX COMMUNITY for the rainfall, temperature and soil of this area This area has not been has not been mowed in about ten years. Shrubs and evergreen trees have moved in. These are the INTERMEDIATE species This area has been mowed within the last year. The plants are all annuals or herbaceous perennials. These are the PIONEER species

Pioneer Species Pioneer species initiate recovery following disturbance in both primary AND secondary successions Pioneers "pave the way" for later colonists by altering the biotic and abiotic environment: soil quantity, quality & depth increased moisture holding capacity light availability temperature exposure to wind Examples: Lichens and mosses

3. DEGRADATIVE (HETEROTROPHIC) SUCCESSION: Sequence of changes associated with DECOMPOSITION processes When organisms die and begin to decompose, a repeated sequence of species appears, characteristic of the organism Since no autotrophs (green plants) are involved in this process, it is also known as HETEROTROPHIC SUCCESSION

Example: When an animal dies, bacteria immediately start breaking down the organic materials. This produces a smell which attracts insects such as flies who lay their eggs on the body. Within a few hours the flies' eggs have hatched and the larvae (or maggots) begin to feed on the animal's soft tissue. Several types of beetle also feed on the dead remains, lay eggs and, when hatched, these larvae will feed on the dead remains as well. Now spiders begin to approach, not to feed on the dead animal, but to feed on the insects which are on the animal's body. The fact that degradative succession always occurs in the same sequence is used by forensic entomologists. These scientists can tell approximately when a victim died because of which insects inhabit the body when it is found

Changes in the complexity of ecosystems As succession takes place, the ecosystem tends to become more COMPLEX and more STABLE Human activities, as well as natural disasters, can reduce the complexity in ecosystems. This reduction in complexity is shown by, for example, a reduction in the number of species present, a decrease in the number and variety of habitats and niches and a decrease in the complexity of food webs

CHANGES IN ECOSYSTEM COMPLEXITY Increase in complexity shown by:  Number of species  Population size  Biological Productivity  Habitat/Niche Variety  Complexity of Food Webs Loss of complexity caused by: Monoculture Eutrophication Toxic Pollution Oxygen depletion AUTOGENIC SUCCESSION ALLOGENIC SUCCESSION DEGRADATIVE SUCCESSION Geophysical Forces (e.g. Climatic Extremes) Associated with Decomposition Primary Secondary Barren Land Colonisation by Pioneer Species e.g. moss, microbes Disturbance of Existing Community

Intensive food production In 1999, the human population reached 6 billion It is estimated that by 2050 this figure will increase to 9.4 billion Sustaining this huge and ever increasing population would not be possible without agriculture. According to the World Health Organisation, over 3.5 million tonnes of food are required every day to provide the minimum calorific intake for today's population and this needs to increase by 83,000 tonnes daily to accommodate the increasing population Since only 11% of land surface is suitable for agriculture, the growing demand for food can only be achieved by increasing productivity

Effects of intensive food production : MONOCULTURE Agriculture or forestry in which a single species is cultivated over a large area for ECONOMIC EFFICIENCY With increased mechanisation and additional use of FERTILISERS and PESTICIDES , farmers can manage larger areas of land Crops are selected for their PRODUCTIVITY (speed of growth/yield) or DISEASE RESISTANCE

Problems With Monoculture The farmer is dependant on fertilisers, fuel, machinery and seed Biodiversity is reduced to maximise crop yield by: REMOVAL of HEDGES – loss of shelter USE of HERBICIDES & PESTICIDES FERTILISERS (can be toxic to other species) By removing natural trees, shrubs etc nutrients can easily leak out of the soil : LEACHING

Simplified ecosystems are vulnerable to difficulties as they represent dense numbers of HOSTS of parasitic or disease-producing organisms E.g. the Irish potato famine of the 1840s was due mainly to the crop’s susceptibility to a particular mould Advantages due to diversity and physical separation are lost RESULTS IN: Potential for mass explosion of pests Over reliance on PESTICIDES This can lead to genetic resistance in pest species … loss of control!

Eutrophication As a result of human activities, sometimes waterways can be polluted by EXCESS NUTRIENTS such as NITRATES and PHOSPHATES These activities include: runoff of animal waste from farms leaching of fertilizer from agricultural areas the addition of untreated sewage This leads to an explosion in the growth of algae producing algal blooms

Oxygen Depletion Although these algal blooms may increase oxygen levels in the water during the day, OXYGEN DEPLETION will occur at night as a result of RESPIRATION As the algae die they accumulate at the bottom of the lake, greatly increasing the number of decomposer organisms, which deplete the oxygen levels further This leaves little oxygen for larger animals which die Eventually species diversity in the water is drastically reduced

Toxic pollution Pesticides and herbicides also contain substances which are toxic to organisms other than those they are intended to kill As well as these substances, many industrial sites are polluted with toxic heavy metals such as LEAD , CADMIUM and MERCURY

Major types of Toxic Pollutants A variety of these toxic chemicals, including unnatural synthetics, have been and are dumped into ecosystems Many cannot be degraded by microbes and persist for years or decades Some are harmless when released but are converted to toxic poisons by reactions with other substances or metabolism of microbes Organisms acquire toxic substances along with nutrients or water, some of which accumulate in their tissues.

Biological Magnification This is the process by which toxins e.g. mercury, poisons, become more and more concentrated with each successive link in a food chain Biomagnification results from biomass at each trophic level being produced from a much larger biomass ingested from the level below. The top-level carnivores are usually most severely affected by toxic compounds released into the environment

Example: DDT The pesticide DDT was used to control mosquitoes and agricultural pests DDT persists in the environment and is transported by water to areas away from the point of application Because it is soluble in lipids and collects in fatty tissues of animals, the concentration is magnified at each trophic level and reached such high concentrations (10 X 10 6 increase) in top-level carnivorous birds that calcium deposition in eggshells was disrupted Reproductive rates declined dramatically since the weight of nesting birds broke the weakened shells

Nuclear Waste The release of radioisotopes by nuclear accidents and the unsafe storage of nuclear wastes also present a serious environmental threat These contaminants can last for many years due to long half-lives and are also subject to biological magnification

Biological Monitoring An INDICATOR SPECIES gives information about the environment in which it is living Species that are known to be sensitive to certain environmental conditions or pollutants can be used to determine the state of an ecosystem by their presence or absence from it Although all species indicate something about the environment in which they live, a few key species are generally used as indicator species e.g.

Biochemical Oxygen Demand (BOD) Oxygen depletion caused by aerobic decomposition seriously affects the freshwater ecosystem The extent of this pollution can be assessed using the BIOCHEMICAL OXYGEN DEMAND (BOD) test that measures the amount of dissolved oxygen in water The BOD test is a mandatory water quality test used to estimate the amount of biodegradable organic material there is present in water A HIGH BOD indicates a HIGH LEVEL of organic pollution in the water. As there is a significant amount of organic matter present in the water a lot of oxygen is required by the micro-organisms to degrade it. A LOW BOD indicates a LOW LEVEL of organic pollution in the water. Less oxygen is required by the micro-organisms because less organic matter is present in the water The mass of dissolved oxygen, in grams per cubic metre or milligrams per cubic decimetre, taken out of solution by a water sample incubated in darkness at 20°C for five days

Increase in Energy Needs The biological world is driven on almost entirely on SOLAR RADIATION captured by plants Major sources of primary energy for humans: FOSSIL FUELS, NUCLEAR FUELS and HYDROPOWER Each form of energy generation has its own environmental consequence Renewable energy sources harness energy without depletion e.g. SOLAR, WIND, WAVE, HYDROGEN, BIOMASS ENERGY PRODUCTION

Environmental Consequences Intensive production of potentially toxic waste Fossil fuels are finite and must be conserved Burning of fossil fuels produce many polluting gases: SULPHUR DIOXIDE NITROUS OXIDE CARBON DIOXIDE WATER METHANE CFCs The release of ‘greenhouse gases’ increases the vital, natural greenhouse effect leading to global warming and thus climatic change ACIDIC GASES GREENHOUSE GASES

The Greenhouse Effect The greenhouse effect is a natural phenomenon and is responsible for maintaining the planet’s temperature 33°C higher than would otherwise be the case, thus allowing life to exist It is caused when sunlight reaches the Earth’s surface, which is converted into heat. This heat is re-radiated back into space in the form of infra-red radiation Although visible light passes through the atmosphere, some of the infra-red radiation is absorbed by the so-called greenhouse gases

Carbon dioxide is the more important greenhouse gas Its contribution is more than all the other greenhouse gases put together Relative contribution of gases to the greenhouse effect

Because of the huge increase in the production of greenhouse gases in the last 150 years or so, the greenhouse effect is increasing and this is thought to be contributing to GLOBAL WARMING . Why is this important?

Global Warming The biological effects of the resulting climate change will have an profound effect on ecological niches and the species that live in them Rising global temperatures will bring changes in: Weather patterns (warmer temps, wetter winters, drier summers, less snow) Polar ice caps melting leading to rising sea levels & flooding of coastal areas Increased frequency and intensity of extreme weather events (hurricanes, floods, droughts) Food shortages Increased spread of disease e.g. malaria

Climate change is already happening! Globally, the ten hottest years on record have all occurred since the beginning of the 1990s Current climate models predict that global temperatures could warm from between 1.4 o c to 5.8 o c over the next 100 years, depending on the amounts of greenhouse gases emitted and the sensitivity of the climate system

Example: CORAL BLEACHING An example of the effect of increasing temperature on organisms is exemplified by the phenomenon known as coral bleaching The zooxanthellae provide the coral polyps with nutrients produced by photosynthesis which, along with the nutrients the polyps gain by preying on tiny planktonic organisms, enables the coral to grow and reproduce quickly enough to produce reefs. The coral in turn provides the algae with a protected environment and a steady supply of carbon dioxide for photosynthesis. The tissues of the corals themselves are transparent - their colours come from the zooxanthellae living inside them. Under stress e.g. rise in sea temp, corals expel their zooxantheallae , which leads to a lighter or completely white appearance, hence the term "bleached" The corals that form the structure of the great reef ecosystems of tropical seas depend on a symbiotic relationship with photosynthesizing unicellular algae called ZOOXANTHELLAE that live within their tissues

End of UNIT 2 !!! Watch DVDs: An Inconvenient Truth’ : Climate Change Planet Earth: The Future Blue Planet : Deep Trouble NAB & A/B Test : Thursday 19th Feb

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