Figure 4.5 Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all but those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace the nonresistant bacteria.
Figure 4.6 Over millions of years, the earth’s continents have moved very slowly on several gigantic tectonic plates. This process plays a role in the extinction of species, as land areas split apart, and also in the rise of new species when isolated land areas combine. Rock and fossil evidence indicates that 200–250 million years ago, all of the earth’s present-day continents were locked together in a supercontinent called Pangaea (top left). About 180 million years ago, Pangaea began splitting apart as the earth’s tectonic plates separated, eventually resulting in today’s locations of the continents (bottom right). Question: How might an area of land splitting apart cause the extinction of a species?
Ecosystems & Biodiversity
Structure of Biosphere
– Species – reproductive group
– Population – members of a single species that
live in a given area
– Community – assemblage of interacting
species in a given area
– Biome – a region with a characteristic plant
community (e.g. rainforest, desert)
– Ecosystem – a community of animals, plants,
microbes, etc. together with the physical
environment that supports it
Green: Grassland Purple: Taiga Orange: Tundra Black:
Temperate Forest Yellow: Desert Brown: Chaparral White:
Geography, weather, climate and geologic
factors influences interactions within an
Organisms of Ecosystems
• Abiotic : Nonliving physical factors of an
environment. It includes water, oxygen,
temperature, amount of sunlight and water
• Biotoic: Living physical factors of an
environment. Examples: Parasitism, disease
• List three more examples of
Abiotic & Biotic Factors:
Second Law of Thermodynamics
• There is a tendency for numbers and quantities of
biomass and energy to decrease along food chains.
• The pyramids become smaller at the top because
around 90% of the energy is “lost” between each
level and only 10% is available in the body of the
organism for transfer to the next level.
– Recent studies indicate that human
activities have approximately doubled the
worldwide supply of fixed nitrogen, due
to the use of fertilizers, cultivation of
legumes, and burning.
– Possible outcome
• increase nitrogen oxides in the atmosphere
• Contribute to atmospheric warming
• Depletion of ozone
• Acid rain.
• Accelerated pollution of lakes.
– Human intrusion has disrupted freshwater ecosystems
by what is called cultural eutrophication.
• Sewage and factory wastes, runoff of animal wastes from
pastures and stockyards have overloaded many freshwater
streams and lakes with nitrogen.
• This can eliminate fish species because it is difficult for
them to live in these new conditions.
Biological and geologic processes move nutrients between
organic and inorganic compartments
• Human activity intrudes in nutrient cycles by
removing nutrients from one part of the biosphere
and then adding them to another.
• Agricultural effects of nutrient cycling.
Human population disrupts chemical cycles
In agricultural ecosystems, a large amount of
nutrients are removed from the area in the crop
• After awhile, the natural store of nutrients can
• The rates at which nutrients cycle function in
ecosystems are extremely variable as a result of
variable rates of decomposition.
– Decomposition can take up to 50 years in the tundra,
while in the tropical forest, it can occur much faster.
– Contents of nutrients in the soil of different
ecosystems vary also, depending on the rate of
absorption by the plants.
Decomposition rates largely determine the rates of
Nutrient cycling is
strongly regulated by
Measurements (Co2 & Temp) in 1958 read 316 ppm and
increased to 370 ppm today
• Life on earth is protected from the damaging
affects of ultraviolet radiation (UV) by a layer of
O3, or ozone.
• Studies suggest that
the ozone layer has
“thinning” since 1975.
Human activities deplete atmospheric
• Probable Reasons for destruction of ozone layer:
– Accumulation of chlorofluorocarbons, chemicals used in
refrigeration and aerosol cans, and in certain manufacturing
– Increased levels of UV radiation that reach the surface of the
Earth. This radiation has been linked to skin cancer and
• The impact of human activity on the ozone layer is one more
example of how much we are able to disrupt ecosystems and the
• The burning of
oxides and nitrogen
react with water
in the atmosphere
to produce sulfuric
and nitric acids.
Burning fossil fuel: Cause of acid
• Humans produce many toxic chemicals that are dumped
– These substances are ingested and metabolized by the
organisms in the ecosystems and can accumulate in
the fatty tissues of animals.
– These toxins become more concentrated in successive
trophic levels of a food web, a process called
Toxins concentration in successive trophic
levels of food webs
DDT is a colourless,
crystalline, tasteless and
organochloride known for
its insecticidal properties
• Ecosystem will fail if it do not remain
• No community can carry more
organisms than its food, water and
shelter can accommodate.
Why Is It Important?
• The biodiversity found in genes, species,
ecosystems and ecosystem processes is vital to
sustaining life on earth.
Natural Capital: Major Components of
the Earth’s Biodiversity
Biodiversity over time - geologic
• Natural changes due to new species evolving
and becoming extinct
• Extinction events – cleans the slate
– Natural extinction – 90% of species ever alive
are extinct now
Genetic Makeup of a Population
• Populations evolve by becoming genetically
• Genetic variations is the First step in biological
– Occurs through mutations in reproductive cells
– Mutations in other cells can happen , but only
reproductive cell mutations are passed on
– Sometimes a mutation can result in a new genetic
trait that gives it a better chance to survive,
• Can a fish species willfully grow
limbs and fingers if they are
needed to crawl out of the water
onto dry land?
Individuals in Populations with
Beneficial Genetic Traits
• Natural selection: Second step in biological evolution
– Adaptation may lead to differential reproduction
– Genetic resistance in bacteria, cockroaches
• When environmental conditions change, populations
– Become extinct
Most of the normal
replaces the strain
A group of bacteria,
resistant ones, are
exposed to an
Three Common Myths about
Evolution through Natural Selection
• “Survival of the fittest” is not “survival of the
• Organisms do not develop traits out of need or
• No grand plan of nature for perfect adaptation
There is a grandeur to this view of life (evolution)
While this planet has gone cycling on…
Endless forms most beautiful and wonderful
have been and are being evolved
Can you draw similes of evolution to Corporates/ organisations?
Geologic Processes Affect Natural
• Tectonic plates affect evolution and the location of life on
– Location of continents and oceans
– Species physically move, or adapt, or form new
species through natural selection
• Tectonic actions: Earthquakes, Volcanic eruptions can
have profound effects on natural selection
– Change in ecosystem
225 million years ago 135 million years ago
65 million years ago Present
Climate Change and Catastrophes
Affect Natural Selection
• Ice ages followed by warming temperatures
Demise of the giants (Sloth, Saber tooth
• Collisions between the earth and large
– New species
Changes in Ice Coverage in the Northern
Hemisphere During the last 18,000 Years
Science Focus: Earth Is Just Right
for Life to Thrive
• Certain temperature range (closeness to sun)
• Dependence on water
• Rotation on its axis (how fast or slow we spin)
• Revolution around the sun (changes in season)
• Enough gravitational mass (to hold on to the atmos)
The Fossil Record Tells Much of
the Story of Evolution
– Physical evidence of ancient organisms
– Bones, casts, tracks…
– Some reveal what their internal structures
looked like, some their actions
• Have all fossils been discovered?
Fossilized Skeleton of an
Herbivore that walked the Earth
Q1) What is the connection between the
environment and evolution?
Q2) Will humans evolve to a point where we can
survive in space without a spacesuit or any
protective device? Why or Why not?
Q3) how does pollution effect evolution?
How Do Speciation, Extinction, and
Human Activities Affect Biodiversity?
• As environmental conditions change, the balance
between formation of new species and extinction of
existing species determines the earth’s biodiversity.
• Human activities can decrease biodiversity by
causing the premature extinction of species and by
destroying or degrading habitats needed for the
development of new species.
• Through geographic isolation
– Groups of same species become physically
– Migration, physical barriers (volcanoes)
• Through reproductive isolation
– Mutation and change by natural selection occur in
isolated geographic populations long enough
– New species when interbreeding produces only
Geographic Isolation Can Lead to
Science Focus: Humans Have Two Ways to Change
the Genetic Traits of Populations
• Artificial selection
• Genetic engineering, gene splicing
– Privacy issues
– Harmful effects
Species Diversity its Importance
• A major component of biodiversity
– Species richness (diversity in species)
– Species evenness (abundance of each species)
• Diversity varies with geographical location
– Most species-rich communities
• Tropical rain forests
• Coral reefs
• Ocean bottom zone
• Large tropical lakes
• Increases the sustainability of ecosystems.
Variation in species evenness
• Temperate Forest, Western Ghats, chilka lake
Species-Rich Ecosystems Tend
to Be Productive and Sustainable
• Species richness seems to increase
productivity and stability or sustainability
of a location
• More diverse ecosystem, more productive,
• More diverse, more complex web, more
resistant to environmental disturbances
What Roles Do Species Play in
• Each species plays a specific ecological role
called its niche.
• Any given species may play one or more of
five important roles—native, nonnative,
indicator (defines traits of environment), keystone,
or foundation roles—in a particular
Role of Keystone, Foundation
• Keystone species
– Top predator( Sharks, Tigers)
– Loss of keystone species lead to population
crashes of other species in ecosystem
• Foundation species
– Create or enhance their habitats, which benefit
• Elephants (trails)
Species Plays a Unique Role
in Its Ecosystem
• Ecological niche
– Pattern of living, includes everything that affects
survival and reproduction
• Generalist species (mice, humans,
– Broad niche
• Specialist species (Tigers, pandas)
– Narrow niche
Specialist Species and Generalist
Case Study: Cockroaches:
Nature’s Ultimate Survivors
– High reproductive rates
• 10 million annually
– Eat almost anything:
– Finger nail clippings,
electric cords, soap
– Live and breed in all but
– Antennae, knee joints, eyes
Good: food for
Threats to Biodiversity:
Why Are Amphibians Vanishing?
• Habitat loss and fragmentation
• Prolonged drought
• Increase in UV radiation
• Parasites (worms causing increase in birth defects)
• Viral and fungal diseases
• Climate change
• Overhunting (Asia and France)
• Nonnative predators and competitors
Impact of Vanishing Amphibians
• Importance of amphibians
– Sensitive biological indicators of environmental
– Adult amphibians
• Important ecological roles in biological
– Genetic storehouse of pharmaceutical products
waiting to be discovered
Case Study: Why Should We
• Keystone species
– Eat dead and dying fish in the ocean
– Control other populations
– Strong immune systems
• Wounds do not get infected
• Almost never get cancer
• Could help humans if we understood their immune
Case Study: Is the Royal Bengal
Tiger worth saving?
Project tiger: Launched in 1973 by GoI and WWF with 9 tiger reserves
having 268 tigers. In 2001, tiger reserves increased to 27, # of tigers ~1500!!. In
2011, we have 53 tigers reserves. Latest tiger census report released in 2011 by
the National Tiger Conservation Authority, est. tiger population is 1,706. Your
Reflect on these! Source: Wildlife protection society of India
TIGER DEATHS IN 2014
TIGER DEATHS IN 2013
Poaching & 42
LEOPARD DEATHS IN 2014
Poaching & 12
LEOPARD DEATHS IN 2013
Poaching & 110
A tigress believed to have strayed from Jim Corbett National Park, killed its 10th person in six weeks.
Source: CBC News: Feb 10’14. The tiger has been on the prowl across an area spanning some 130
kilometres. "The animal has started attacking humans because it is not getting its natural prey," said Rupek
De, chief wildlife warden of Uttar Pradesh.
•Jumbo concern only gets bigger - In six years, 354 persons killed by elephants in state Orissa, 5th
•Huge number of seized leopard claws puzzles Forest officials, 6th
Why are Tigers important?
• Keystone species
• Presence in food web
• Pathways- keep pathways open, hold back
changes in marshy areas
• Maintain Ecological Balance
– Provide in-situ conservation (protect its habitat with all other
species). Create national Parks & Sanctuaries
– Establish ex-situ conservation (for endangered species give
protection in controlled environment viz. botanical garden for plants & zoological
parks for animals)
Humans: Saviour or Threat to
• Present day rates exceed geological rates of
extinction. Scientists est. that we are likely to eliminate ~ 10Million
species by 2050
• Present day extinction is across the board – affects
• Modern extinction associated with spread of
– Over hunting/fishing
– Habitat destruction – deforestation & coral bleaching
the spread of
Parks & Sanctuaries
Almost 4 % of India's land is under forests. There are 80 national parks and over 441
wildlife sanctuaries in India.
•National parks are formed by Central or State Legislation.
•Status of National Park is higher.
•No human habitation is permitted in the park area.
•Harvesting timbers, cultivation, collection of forest products
are restricted. Eg. Corbet National Park.
•Sanctuaries are formed by the order of State or Central
•Status of sanctuary is lower.
•Private ownership may be allowed.
•Limited activities are allowed with permission. Eg. Chilika-
Sanctuary for migrating birds.
Case Study: Beej Bachao Aandolan (Save the
seed Movement) & livestocks breeding
• Seed Movement began in Himalayan tarai
• Successfully conserved hundreds of local rice varieties.
• Gene banks collected 34000 cereals & 22000 pulses grown
• 27 breeds of cattle &goats, 8 breeds of buffaloes. Many are
dying out due to misguided adoption of ‘foreign’ things
viz: Jerseys & Holsteins
Q1) Distinguish between species richness and evenness
Q2) Suppose we have 2 national parks close to each other
surrounded by development. One is a large park and the
other much smaller. Which park is likely to have the
highest species richness? Why?
1. Are there regions of your country with large amounts of
2. What climate conditions/Geologic features have influence on
natural selection in the major biomes of your country?
3. Indicate some unique indicator, keystone, foundation,
invasive and specialist species that live within the borders of
4. Do the people in your country get most of their food from
within ? Substantiate your answer with examples.
• Q1: What are three ways that the Tigers supports one or more
of the four components of biodiversity within its
• Q2: What are three examples of how people, in their daily
living, intentionally or unintentionally degrade each of these
types of biodiversity?
• Q3: What are the main differences between Functional and
Ecological Diversity? What are the main differences
between species and genetic diversity?
• Q4: Why is having a lot of biodiversity on earth so beneficial
Deforestation and soil nutrients
• Distinct differences in storage of biomass &
nutrient cycling between temperate & tropical
• Temperate forests have thick, rich topsoils
– Humus layer of organic detritus on top of subsoil
– Nutrients stored in soils
• Tropical soils are highly weathered (lots of rain)
– Lateritic clays depleted in nutrients
– Thin humus layer
– Nutrients stored in biomass
Tropical above ground
storage of biomass & nutrients
Deforestation and recovery
• Rainforests – loss of rainforest trees leads to
loss of nutrients & changes in the water
• Temperate forests recover because nutrients
retained in the soils
Deforestation & water cycle & climate
• Elimination of tropical rainforests disrupts regional
– Minimizes evapotranspiration (source of H2O to atm)
– Decreases soil moisture and increases runoff
• Increases erosion rates
– Soils form slowly
– 200-1500 yrs to form 2.5 cm of topsoil from bedrock
• General circulation models to predict
– Net temperature increase
– Decrease in soil moisture
Biodiversity and deforestation in tropical
• Half of the living species are found in rainforests
• Forest plants have medical value
– Treatment of diseases
• Forest plants have agricultural value
– Need genetic diversity for long-term health (Darwinian
– Need variety to limit vulnerability to diseases and pests
– Modern agricultural practices limit diversities
– Centers of genetic diversity for crops come from areas
threatened by development, population pressures,
– Seed banks
Biodiversity and ecosystem stability
• Relationship is complex
– In some settings environmental stability leads to high
– In others, high diversity is thought to result from
disturbances of intermediate frequency and intensity
• How does loss of biodiversity impact ecosystem?
– Remove enough species and ecosystem collapses (removal
of predators; invasive species)
– May be that some species aren’t necessary – system
maintained by a few keystone species
Causes of deforestation
• Social, political, and economic drivers
• Economic arguments – people and countries
need hard currency (Nepal)
– Motivation not to
– Who will bear the costs of not exploiting
• Earth will recover, will humans survive?