Option G Ecology Ecology is the study of ecosystems
Ecosystem is a compilation of both biotic and abiotic factors, how organisms interact with their environment.
Community of different species in the same area which are interacting
Population group of organisms of the same species who live in the same area at the same time
Habitat is the environment in which a species normally lives or the location of a living organism
Distinguish between autotroph and heterotroph .
Autotrophs are capable of making their own organic molecules from inorganic molecules as a food source (a.k.a. producers); Examples?
Heterotrophs – cannot make their own food and must obtain organic molecules from other organisms (a.k.a. consumers); Examples?
Consumers ingest organic matter which is living or recently killed food chains show the flow of energy through the trophic levels of a feeding relationship .
Detritivores (Ingest, then digest) ingests non-living organic matter
Saprotrophs (Digest first, then absorb) live in or on non-living matter, secreting digestive enzymes into it and absorbing digestive products
Trophic Levels of Feeding Groups
Ecologists divide the species in a community or ecosystem into trophic levels based on their main source of nutrition.
Primary producers- autotrophs- produce their own energy source.
Photoautotrophs - derive energy via photosynthesis- plants
Chemoautotrophs- use energy stored in chemical bonds- Sulfur
Consumers - heterotrophs- derive energy from consuming other organisms
1 consumer- eat producers
2 consumer- eats herbivores- 1 consumer
3 consumer- eats 2 and 1 consumers
Decomposers - consume dead material- recycle nutrients back to the environment- Saprotroph
Secondary Productivity- the rate as which an ecosystem ’ s consumers convert the chemical energy of the food they eat into their own new biomass
The efficiency of energy transfer between trophic levels is usually < 20% (≈10%)
Trophic Levels Notice that only 10% is moved to the next level. Where does the rest go?
THE 10% RULE and ECOLOGICAL PYRAMID
Energy Flow Through Ecosystems
Shows more complex interactions between species within a community/ ecosystem
More than one producer supporting a community
A consumer may have a number of different food sources on the same or different trophic levels
What are the factors that effect
Abiotic (nutrients and energy)
Biotic individual organisms that live in that ecosystem
Factors controlling and ecosystem
Nutrients (Closed System)
Energy (Open System)
Interactions between species
I. Nutrient Cycles Through Ecosystems
Biogeochemical cycles are cycles of matter between the abiotic and the biotic components of the environment
The carbon, nitrogen , phosphorus, and water cycles are central to life on Earth
Carbon, nitrogen, and water cycles have atmospheric components, and cycle on a global scale
Phosphorus has no atmospheric component, and cycles on a local scale
Very few types of organism play a role in the cycling of nutrients Saprotrophic Bacteria cycle Nitrogen Fungi Cycle Carbon
Is exchanged of the element carbon among the biosphere. Or geosphere, hydrosphere, and atmosphere of the Earth.
Carbon interconnected by pathways of exchange with these reservoirs is mainly through plants .
Extended from 359 million years ago, to the about 299.
A time of glaciation, low sea level and mountain building. With many beds of coal were laid down all over the world during this period.
The world’s large coal deposits occurred during this time period.
1. The appearance of bark-bearing trees
(containing bark fiber lignin ).
2. Lower sea levels
Development of extensive lowland swamps and forests .
Large quantities of wood were buried during this period.
Animals and decomposing bacteria had not yet evolved that could effectively digest the new lignin.
Appear 290 million years ago . They can degrade it Lignin . The substance is insoluble, to heterogeneous because of specific enzymes, and toxic, they are one of the few organisms that can.
II. Energy (Open system on Earth)
Hubbard Brook Experimental Forest
Hubbard Brook Experimental
Found that 1,200,000 of kcal of energy hit the Earth from the Sun per sq. meter (or about enough energy to light a 150watt light bulb continuously).
Photosynthetic plants were only absorbing about 10,000 kcal per sq. meter and converting in organic material sometimes called the primary production. (or enough energy to power a 1.5 watt light bulb continuously).
Sunlight is the initial energy source for almost all communities
Energy flows through the food chain, being lost at each stage due to respiration.
Pyramids of energy
Show the flow of energy between trophic levels
Measured in units of energy per unit area per unit time. KJ m -2 y -1
The transfer of energy is never 100% efficient
Energy Flow through the Ecosystem
The conversion of light energy into energy stored in chemical bonds within plant tissue. Primary production results in the addition of new plant biomass to the system.
Net Primary Production
Gross Primary Production .
The most productive terrestrial areas are tropical rain forests; least productive are deserts
NPP = GPP - R
Gross Primary Production (GPP) is the amount of light energy that is converted to chemical energy by photosynthesis per unit time.
Net Primary Production (NPP) is equal to gross primary production minus the energy used by the primary producers for respiration (R). Which will be the total energy available to all the other living things in that ecosystem
Biomass is the total dry mass of organic matter in the organisms or ecosystem.
By measuring biomass of an ecosystem we can see how productive it is and compare this to other ecosystems of past data
Pyramids of Biomass
The movement to a stable ecosystem
Ecosystems are not fixed, but constantly
change with time. This change is called
succession . Imagine a lifeless area of bare
rock. What will happen to it as time passes?
What Occurs during Succession?
Produced by detritivores (worms) following death of other plants and animals
Detritivores and bacteria fix nitrogen and other inorganic nutrients into the soil
Bind the soil, preventing erosion
Support larger plans
Uptake, filter and recycle massive amounts of water.
starts with bare rock or sand, such as behind a retreating glacier, after a volcanic eruption, following the silting of a shallow lake or seashore, on a new sand dune, or on rock scree from erosion and weathering of a mountain.
Gross production increases
First colonizers are lichens on rock surfaces
Soil builds up following death of smaller lichens
Productivity plateaus as soils carrying capacity is reached
Species diversity increases
More soil allows for burrowers, worms and detritivores
More plants take root and provide mew niches
More deaths leads to more soil and nutrient recycling
Very few species can live on bare rock since it stores
little water and has few available nutrients. The first
colonizers are usually lichens. Colonizers start to erode
the rock and so form a thin soil.
G rasses and ferns grow in the thin soil and their roots accelerate soil formation. They have a larger photosynthetic area, so they grow faster
Dandelion, goosegrass “weeds” have small wind-dispersed seeds and rapid growth, so they become established before larger plants.
Larger plants ( Small trees and large shrubs)
bramble, gorse, hawthorn, broom and rhododendron can now grow in the good soil. These grow faster and so out-compete the slower-growing pioneers.
Trees grow slowly, but eventually shade and out-compete the shrubs, which are replaced by shade-tolerant forest-floor species. A complex food web is now established with many trophic levels and interactions. This is called the climax community .
• Starts with soil, but no (or only a few) species, such as in a forest clearing, following a forest fire, or when soil is deposited by a meandering river
Picture right after a forest fire One year later Five years later
Primary vs. Secondary Succesion
Is made up of all the world’s biomes. Biomes are simply component of the larger unified ecological system, the biosphere
Climatically and geographically defined areas of ecologically similar characteristics. Temperature and rainfall are key abiotic features of each biome and plant and animal species are adapted to survive in the available niches.
Rainfall and Temperature Affect the Distribution of Biomes.
Biomes of the World
How many biomes are there?
Temperate Deciduous Forest
Although there is some disagreement among scientists on how to divide up the Earth’s biomes, most can agree on the following six:
Means treeless or marshy plain
Characterized by permafrost – permanently frozen soil starting as high as a few centimeters below the surface – which severely limits plant growth
Low temperature , winter temperatures average –34 o C while summer temperatures usually average below 10 o C
Low precipitation (15–25 cm per year) but ground is usually wet because of low evaporation
Typically found between 25 o and 40 o latitude
Receives less than 25 cm of rain each year
Temperatures typically range between 20 o C and 25 o C but some extreme deserts can reach temperatures higher than 38 o C and lower than –15 o C
Found between 32 o and 40 o latitude on the west coast of continents
Receives between 35 and 70 cm of rain, usually in the winter
Extremely resistant to drought and weather events
Because of the dry climate, trees are found only near water sources such as streams
Usually receives between 50 and 90 cm of rainfall each year
Summer temperatures can reach up to 38 o C, and winter temperatures can fall to –40 o C
Temperate Deciduous Forest
Most trees will lose their leaves in the winter
Temperatures range between –30 o C and 30 o C
Averages from 75 to 150 cm of precipitation
Well developed understory
Typically found near the equator
Receives more than 200 cm of rain annually
Temperatures typically fall between 20 o C and 25 o C for the entire year
As many as 50% of all the world’s animal species may be found here
III. Interactions between species
G 1.2a Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory.
G 1.1a Outline the factors that affect the distribution of plant species, including temperature, water, light, soil pH, salinity and mineral nutrients.
G 1.2b Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory.
G 1.2c Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory.
G 1.2c Explain the factors that affect the distribution of animal species, including temperature, water, breeding sites, food supply and territory.
Interactions Between Species
Competition is when two species need the same resource such as a breeding site or food. It will result in the removal of one of the species. There are two major types of competition
I. Intraspecific competition
A form of competition in which individuals of the same species compete for the same resource in an ecosystem. This tends to have a stabilizing influence on population size. If the population gets too big, intraspecific population increases, so the population falls again.
II. Interspecific competition
A form of competition in which individuals of different species compete for the same resource in an ecosystem.
A. Predation is the relation between the predator, which is usually bigger, and the prey, which is usually smaller. An example would be a fox and a rabbit
B. Parasitism is the relation between the host and the parasite. The parasite causes harm to the host to get food and other resources. Examples of parasites are some viruses, fungi, worms, bacteria, and protazoa.
C. Mutualism is where two members of different species benefit and neither suffers. Examples include rumen termite/protazoa that digest cellulose
Primary Consumers that feed only on plant material. Considered predators of plants. Ladybug and a caterpillar are examples of herbivories
Organisms devised methods of reproduction to deal with species interactions
r-strategies “real lot”
An r-strategy involves investing more resources into producing many offspring, having a short life span, early maturity, reproducing only once and having a small body size.
Frog Eggs Frogs lay many eggs & leave them in the water to hatch into tadpoles, some get eaten, some become tadpoles.
Tadpole Some tadpoles are eaten, some tadpoles become frogs
Frog Many animals are waiting on shore for frogs: raccoons, foxes, and many other small predators. If 1 frog from a 100 eggs lives to be a parent, his/her survival is really outstanding
A K-strategy involves investing more resources into development and long-term survival. This involves a longer life span and late maturity, and is more likely to involve parental care, the production of few offspring, and reproducing more than once.
Where does a species fit on the r-k spectrum?
Some organisms have both r and K stages or characteristics, such as large trees, sea turtles and many other reptiles
Some species, such as Drosophila, change strategies depending on environmental conditions
r and K strategists favor different enviromental conditions
Unstable, changing environments provide opportunities for fast reproducing organisms.
Early primary or secondary secession provide opportunities for these species
In stable, predictable environments it is more effective to invest resources in becoming more competitive.
Macrofauna and flora are more abundant in stable, long established ecosystems and havitats after much of succession of species.
A population’s niche refers to its role in its ecosystem .
This usually means its feeding role in the food chain .
A description of a niche should really include many different aspects such as its food, its habitat, its reproduction method and the organisms it interacts with.
Identifying the different niches in an ecosystem helps us to understand the interactions between populations. Members of the same population always have the same niche, and will be well-adapted to that niche.
No two species in a community can occupy the same niche
Species A niche Species B niche
Principle of Competitive Exclusion
Where two species need the same resources and will compete until one species is removed.
One would be more capable of gathering more resources or reproducing more rapidly until the other was run out of existence.
Experiments with paramecium populations in the lab of Ecologist G.F. Gause demonstrated this concept scientifically.
The niche concept was investigated in some classic experiments in the 1930s by Gause . He used flasks of different species of the protozoan Paramecium , which eats bacteria and yeast .
Conclusion: These two species of Paramecium share the same niche, so they compete. P. aurelia is faster-growing, so it out-competes P. caudatum .
P. aurelia P. caudatum
In the second experiment he took P. caudatum and had it compete with a second type of Paramecia. It is important to understand the distribution in experiment 2.
P. caudatum lives in the upper part of the flask because only it is adapted to that niche and it has no competition. In the lower part of the flask both species could survive, but only P. bursaria is found because it out-competes P. caudatum .
Conclusion : These two species of Paramecium have slightly different niches, so they don't compete and can coexist.
Fundamental vs. Realized Niche
Fundamental Niche : the potential mode of existence, given the adaptation of the species
Realized Niche : the actual mode of existence, which results from its adaptations and competition with other species
Competition II Competition I Competition III Realized Niche
The total number of individuals of a species in a given area.
Populations are affected by four main factors
Four Factors Influence the Size of a Population:
Natality: Birth Rate (offspring produced and added to population)
Mortality: Death Rate (individuals that die)
Immigration: Movement of members of the species into the area
Emigration: Movement of members of the species out of area to live elsewhere.
Exponential growth Phase
Limited Growth Sigmoid (S-Shaped)
1. Exponential Growth Phase
Population increases exponentially.
Resources are abundant.
Predators and disease are rare .
2. Transitional Phase
As a result of intra-specific competition
for food, shelter, nesting space, etc.,
and the build up of waste.
The growth rate slows down.
Birth rates decline and death rate increases
3. Plateau Phase
Natality and mortality are equal so population size is constant.
When the number of individuals in the population have reached the maximum which can be supported by the environment.
The number is called the CARRYING CAPACITY
Population size oscillates around the carrying capacity ( K) Time N K overshoot oscillations
Density Dependent Limits
Density Independent Limits
Humans (logging, mining, farming )
Water and shelter are critical limiting factors in the desert. Fire is an example of a Density independent Limiting factor. Limits on Population Growth
How did we get here?
When I graduated
high school there were
4 billion people.
Today there are
almost 7 billion people
About 5 million years ago Hunter-gathers 1 million people
Neolithic Period (6000 B.C.) No longer a Natural Setting 100 million people
Common area 2000 years ago 300 million people
1800’s (Carbon cycle control) Steam engine 1 billion people
London between 1800 to 1880
1800 pop. 1 million
1880 pop. 4.5 million
Improvements in medicine and public health
Neolithic it was 20
1900 it was 30
1950 it was 47
Current world average is 67
From 1 billion to 6 billion? How???
1908 Control of the Nitrogen Cycle
Up until 1908 farms were dependent on organic sources for nitrogen (manure)
Haber figured out how to convert N 2 into NH 3 and then into NH 4 + of NO 3 -
Commercial fertilizers are born
1944 Plant Breeding
Disease resistance improvements
Less day-length sensitive
Improve sharing of ideas on plant breeding
What’s Behind Population Growth
Animal Domestication and Agriculture
Provided for a few to feed many
Growth of Cities and Infrastructure
Exponential growth of the human population Human population growth does not currently show density effects that typically characterize natural populations. Limited resources eventually will cause human population growth to slow, but global human carrying capacity is not known.
Most predictions: 9-12B by 2050 10-15B by 2100
Deforesting to acquire more arable land
Would run out in next century at current yields
In 1950 people used half of accessible water
Are now dependent on dams
Pollution loses 33% of potential water
Getting close to limits
growth very high last fifty years
Mostly hydrocarbon fuels
Nonrenewable resource consumption
Climate change issues
Why monitor populations ?
Determine current status of a population
Determine habitat requirements of a species
Evaluate effects of management
*Complete “census” of natural populations is often very difficult!
Population vs. Sample Sample True Population
A sampling procedure that assures that each element in the population has an equal chance of being selected
Sampled population should be representative of target population
There are MANY more…
A square frame is placed in a habitat
All the individuals in the quadrat are counted
The process is repeated until the sample size is large enough
Useful for small organisms or for organisms that do not move
Converting a population study into a graph
MARK-RECAPTURE (Lincoln Index)
Capture and mark known number of individuals
2 nd round of captures soon after
Time for mixing, but not mortality
Fraction of marked individuals in recapture sample is estimate of the proportion of population marked in first capture
Paint or dye
Large mammals; keep photo record
Reptiles, amphibians, rodents
Using mark-recapture sampling to estimate animal populations
Population Size P =( # initially marked) x (total 2 nd catch)
(# of marked recaptures)
N 1 x N 2
Mark Recapture Lincoln Index N 1 = 4 N 2 = 5 N 3 = 2 N 1 = first capture N 2 = second capture N 3 = #’s of marked in second capture
Survey 1: N 1 = 12 Survey 2: N 2 = 15 N 3 = 4
You capture and mark 150 fish in a lake. (This must be a random, representative sample.)
You release them back into the lake, allowing enough time for them to remix with the population.
You trap another 220 fish, of which 25 are recaptures (i.e., marked from the initial trapping.
What is your estimate of the total population of fish in the lake?
N 1 = 150
N 2 = 220
N 3 = 25
P = [(220)(150)] / 25
= 1320 FISH
Use the Lincoln Index to monitor this mountain gorilla population over time
Human Effect on the World Fish Population
Overexploitation of species affects the loss of
genetic diversity and the loss in the relative
species abundance of both individual and/or groups of interacting species. Overexploitation may include over fishing and over harvesting
Historically, humans have fished the oceans, which never seemed to pose a problem due to their abundant resources. Gear (fish trap, gill nets, electro-fishing) and vessel efficiency modifications have caused a significant decrease in fish populations.
A case study: The Peruvian Anchovy ( Engraulis ringens ) Universidad de La Serena
The Peruvian Anchovy
This is a small (12-20cm), short-lived species maturing in 1 year
Anchovy live in the surface waters in large shoals off the coast of Peru and northern Chile
Here there are cold currents up-welling from the sea bed bringing nutrients for phytoplankton
Plankton is at the base of the food chain.
The Peruvian Anchovy
The harvest of this fish doubled every year from 1955 to 1961
Experts estimated the maximum harvestable yield ( MSY ) at 10 to 11 million tonnes per year
Through the 1960s the harvest was about this level
The biggest fishing harvest in the world
Some of the anchovy were used for human food
But a lot was ground into fishmeal for animal feed
The collapse of the anchovy fishery
In 1972 there was an El Ni ñ o event that brought warm tropical water into the area
The up-welling stopped,
the phytoplankton growth decreased
the anchovy numbers fell and concentrated further south
The concentrated shoals of anchovy were easy targets for fishing boat eager to recuperate their harvest
The political will was not there to impose reduced quotas
Larger catches were made
No young fish were entering the population (no recruitment)
No reproduction was taking place
The fish stocks collapsed and did not recover
Population dynamics of fisheries
A fishery is an area with an associated fish population which is harvested for its commercial or recreational value. Fisheries can be wild or farmed.
Population dynamics describes the ways in which a given population grows and shrinks over time, as controlled by birth , death , and emigration or immigration . It is the basis for understanding changing fishery patterns and issues such as habitat destruction , predation and optimal harvesting rates .
The population dynamics of fisheries is used by fisheries scientists to determine sustainable yields
Estimating Fish populations
Fish Catch Data The total volume of the catch (in tons). The catch rate (number of times fishing). The catch rate by age of the fish.
Technology The use of echolocation and satellite images can be used to track and estimate populations
Lincoln Index (Capture-Mark-Recapture ) day one, mark and release the fish. The next day, repeat the sequential sampling and also records the total number of fish marked and unmarked so we can use to estimate of fish population density
The overall catch has decreased fish stocks in many areas of the United States, as catches in each area exceed the maximum number of fish that these fishermen are allowed to take.
Maximum Sustainable Yield (MSY)
the harvest rate
the recruitment rate of new (young) fish into the population
a population can be harvested at the point in their population growth rate where it is highest (the exponential phase)
Harvesting (output) balances recruitment (input)
Fixed fishing quotas will produce a constant harvesting rate (i.e. a constant number of individuals fished in a given period of time)
Maximum Sustainable Yield (MSY) K
Time 1 2 3
Maximum Sustainable Yield
The Largest possible catch without adversely affecting the ability of the population to recover.
Problems with MSY
Age structure : If all the age groups are harvested recruitment of young fish into the reproductive group will be reduced. The answer is to use a net with a big enough mesh size that lets the young fish escape
Limiting factors : If the limiting factors in the environment change so does the population growth rate
Limiting factors set the carrying capacity (K) of an environment
Increasing limiting factors will cause K to drop
Fixed quotas cannot cope with this
Data: For MSY to work accurate data in fish populations is needed (population size, age structure, recruitment rates)
Usually these are not well known
What is required?
Nets with bigger mesh size
Regulated fishing methods
More data on fish populations (e.g. by fish tagging investigations – mark and recapture)
Constant monitoring to observe changes in environmental factors (e.g.El Ni ñ o events
Policing of fishing industry – respect of quotas
Greater exploitation of fish farming
But this is not without its own problems (space, diseases and pollution are all associated with intensive fish culture)
4 Serious Environmental Issues
Reduction in Biodiversity
Greenhouse Effect (Global Warming)
1. Reduction in Biodiversity
Simpson diversity index
The index of diversity is used as a measure of the range and numbers of species in an area. It usually takes into account the number of species present and the number of individuals of each species. It can be calculated by the following formulae:
D = N(N-1) ∑n(n-1)
D= Diversity index
n = number of individuals of a each species found in an area.
N = total # of organisms of all species found in an area.
The simpson diversity index is a measure of species richness.
A high value of D suggests a stable and ancient site.
Comparing both indices, 6.05 is an indicator of greater
diversity. The higher number indicates greater diversity
Abiotic factors for Biodiversity
In extreme environments the diversity of organisms is usually low (has a low index number). This may result in an unstable ecosystem in which populations are usually dominated by abiotic factors . The abiotic factor(s) are extreme and few species have adaptations allowing them to survive. Therefore food webs are relatively simple, with few food chains, or connections between them – because few producers survive.
Abiotic factors for Biodiversity
In less hostile environments the
Diversity of organisms is usually high
(high index number). This may
result in a stable ecosystem in which
populations are usually dominated by
biotic factors , and abiotic factors are
not extreme. Many species have
adaptations that allow them to
survive, including many
food webs are complex, with many
inter-connected food chains.
The use of biotic indicator for monitoring environmental change
Are a good indicator of change
Highly sensitive to environmental changes
Highly sensitive to population increases or decreases.
The numbers of organisms in the indicator species populations, can be measured directly so they are easy to keep track of larger changes that maybe occurring.
Feeds on aquatic insects and their larvae, including dragonfly, nymphs and caddisfly larvae. It may also take tiny fish.
The presence of this indicator species shows good water quality; it has vanished from some locations due to pollution or increased silt load in streams
Humans Contribute to Declining Biological Diversity
Introduction of exotic species harms native species due to competition, predation, or interbreeding
The zebra mussel from the Caspian, introduced into the American Great Lakes These mussels not only cause billions of
dollars of damage but have displaced the native clams and mussels
Asian long-horned beetle
Discovered in the US in 1996 on several hardwood trees (destroying the hardwood tree) in Brooklyn, NY. The wood-boring beetle is believed to have been introduced on wood pallets and wood packing material in cargo shipments from Asia. The infestation quickly spread to Long Island, Manhattan and Queens
A wetland plant species found in every U.S. state (crowding out the native species).
It can grow up to 6 meters high in dense stands and is long lived. The species is invasive particularly in the eastern states along the Atlantic Coast and increasingly across much of the Midwest and in parts of the Pacific Northwest.
Rabbits as an invasive species
Rabbits were brought to New Zealand and released for both food and sport at various sites as early as the 1830s
Once rabbits became established, their population increased to plague proportions
Their impact has been little short of an ecological disaster, as the vegetation grazed off by rabbits may never recovered.
Example of a biological control of invasive species.
Example : RHDV (rabiit haemmorragic disease virus) has been introduced to in order to control the population of rabbits.
Solution : Introduce RHDV, a virus specific to the rabbits. Tested under quarantine first (to ensure safety), then released into the wild populations. Adult rabbit contract spreads the virus, but it does not affect any other species.
Effectiveness : Very effective, though some evidence of RHDV resistance in rabbits is starting to become apparent.
The Conservation of Biodiversity
Biodiversity is highest in the Tropical Rainforest
Four Reason for conservation of the tropical rainforest
Ethical reasons for conserving biodiversity are that all species have a right to live on this planet.
Ecological reasons are that species live with great interaction and dependence on each other. If one species dies out, a food chain is disrupted, therefore disrupting all of the other species as well.
Economic reasons are that the rainforest is a source of materials important to human life. Medicinal substances can be taken from a variety of plants in the rain forest, and ecotourism offers a new source of funds for the many impoverished nations these forests exist in .
IV. Aesthetic reasons are that the tropical rain forest is one of the most beautiful attractions on this planet. There is variety everywhere in the rainforest.
The cause and the consequences of biomagnification
A process in which chemical substances become more concentrated at each trophic level.
As each individual eats contaminated food or filters contaminated water, it is building up these substances.
When a large number of contaminated individuals are eaten, they pass on a high concentration of chemicals to the predator.
An example of biomagnification
Biomagnification of DDT
Cause: DDT is a synthetic pesticide sprayed on crops and can be used against malaria mosquitoes. It is washed into waterways in low concentrations, where it is biomagnified up the food chain. It is highly toxic at high concentrations.
Consequences: Stored in fats and accumulates quickly. Very high concentrations in large fish and seabirds. It is responsible for reduced reproductive function and shell thinning in birds, which has impacted populations of large birds of prey heavily. In humans, it has been linked with cancers, fertility and developmental problems.
An example of biomagnification
3. The ozone layer in the stratosphere absorbs UV radiation
Ultraviolet Radiation and the Ozone Layer
With a depleted ozone layer, more UV radiation will reach the surface of Earth
This will cause an increase in many problems, including cancer, will affect crops, damage phytoplankton and zooplankton
Chlorofluorocarbons ( CFCs)
Certain chemicals destroy stratospheric ozone
Chlorofluorocarbons ( CFCs) are broken down by UV in the stratosphere and react with ozone, forming molecular oxygen
CFCs are not used up in this reaction, and are able to break down many thousands of ozone molecules
Ozone Depletion Is Harmful
Ozone depletion harms living organisms
Exposure to UV is linked to disorders in humans, including cataracts, skin cancer, and weakened immune systems
Exposure to increasing UV is linked to declines in phytoplankton productivity
Basal Cell Skin Cancer
6% Declines in phytoplankton over the last 10 years map right: Satellites Many of the areas showing an increasing trend appear along the coasts, in red, while most of the dark blue areas indicate a decreasing trend. Units for the top two panels are milligrams of chlorophyll per cubic meter.
4. Greenhouse Effect ( Global Warming)
The Greenhouse Effect
The Greenhouse Gases
How the greenhouse effect works
Sunlight enters Earth’s atmosphere b/c the gases of the atmosphere are transparent to light
Most is reflected off surface
Some is transferred into heat energy and warms the planet which in turn radiates much back to the atmosphere
Greenhouse gases trap heat in atmosphere
The Greenhouse Effect
The molecules of some gases in the atmosphere absorb heat energy and retain it
This can be a good thing
Without an atmosphere the Earth would have same temperature as the moon
Moon mean surface temperature -46°C
Moon temperature range: -233 to +123°C
Earth is undergoing global warming b/c human-generated greenhouse gases are causing the atmosphere to retain more and more heat
Carbon, methane, and oxides of nitrogen are main culprits