Transcript Unit 3- Biodiversity

Biological Diversity
What is it?
• The wealth of species that live on the Earth
• This includes individual species, habitat,
genetic varieties, or the number or abundance
of species
Biological Evolution
• This is the change in inherited characteristics
of a population from generation to generation
What causes Evolution?
1. Competition for resources
2. Ability to adapt to environmental conditions
• As the environment changes, so to do the
species that live there
Unifying Principles of Evolution
• Perpetual Change: All species are in a
continuous state of change
How does Evolution Occur?
1. Natural Selection
• The process of increasing the proportion of
better adapted offspring
• Mutations create variations which may lead to
better adapted individuals better suited for
the environment
• These organisms then
reproduce, passing along
these better genes
Darwinian Natural Selection
• Three conditions necessary for evolution by
natural selection to occur:
– Natural variability for a trait in a population
– Trait must be heritable
– Trait must lead to differential reproduction
• A heritable trait that enables organisms to
survive AND reproduce is called an
adaptation
How Does Evolution Occur?
2. Migration (Gene Flow)
• The movement of organisms (and genetic
makeup) from area to another
• Can become geographically isolated leading to
divergent evolution. This is when two
organism, isolated from one another for long
periods of time, become genetically different
Example of Migration
Emu vs. Ostrich vs. Rhea
Australia
Africa
South America
When faced with a change in environmental condition,
a population of a species can get MAD:
– MIGRATE to a more favorable location
– ALREADY be adapted
– DIE
• Natural selection can only act on inherited alleles
already present in the population—do not think that
the environment creates favorable heritable
characteristics!
• Soooo….how do new alleles arise??????
MUTATIONS, MY FRIENDS!
• Changes in the structure of the
DNA
• Adds genetic diversity to the
population
• May or may not be adaptive
– Depends on the environment!
How Does Evolution Occur?
3. Mutation
• This is when an organisms DNA is altered
somehow.
• This changes the organisms genotype or
genetic makeup
• Mutations can be advantageous,
disadvantageous, or neutral
4. Genetic Drift
• These are changes in population due to
chance
• Chance does not take sides and does not
necessarily help the better adapted to survive
Island Ecology
• Islands have fewer species on them
• Smaller islands and island farther away have
even fewer
• Example – Galapagos Islands
• Darwin observed many different finch
populations on the island and concluded they
all came from a single species
• This was know as Adaptive radiation. Each
finch has a specialized role
• The finches different beaks are specialized for
different food sources
• Problem is that small populations can be
easily wiped out by storms, floods, disease,
climate change or predators
• Most island contain smaller sized animals.
This is due to the fact that resources are
limited. Being small requires less energy to
survive
• Homo floresiensis – dwarf humans found on
the island Flores in Indonesia
• 3-4 feet tall
• May have become extinct due to volcanic
eruptions
• Ecological Island – small amount of habitat cut
off from other large segments of habitat
• Example – Rock Cut State Park
Number of Species
• Thought to be between 3-10 million, but truly
not known
• Why? New species are discovered and go
extinct all the time
• Insects – 500,000 species
• Plants – 230,000 species
• Mammals – 4500 species
Why are there so many species?
• Each has different ecological niches
1. More complex the habit, the more
biodiversity
2. Topography increases biodiversity
Ex. Hills, mountains, hotter and wetter climates
3. Wildfires can increase biodiversity
4. People affect biodiversity
-Urbanization decreases biodiversity
Threatened and Endangered
Some numbers that are in danger of extinction:
• 23% of mammalian species
• 12% of birds
• 4% of reptiles
• 31% of amphibians
• 3% of plants
• Endangered species – a species that is on the
verge of becoming extinct
• Threatened species any species that is likely
to become endangered
• Local extinction – when a species disappears
from part of its range but can be found
elsewhere
• Global extinction – when a species can no
longer be found anywhere on the planet
Why save them?
1. A symbol of wilderness
2. So that habitats can manage themselves and we
can observe natural habitats
3. Save genetic variation in the wilderness
4. Save genetic material for future use
5. Also don’t forget about the four justifications
(Moral, Aesthetic, Utilitarian, Ecological
Extinctions
• Throughout Earths history there have been
mass extinctions
• Some species exist for hundreds of million
years, other for just a few million
• Six major mass extinctions have occurred in
the past 550 my.
Hey Dinosaurs, what happened?
• 65 mya
• Evidence suggest that an asteroid hit the earth
• This impact caused food chains to break down
and many animals could not adapt.
More recent extinctions
• 20-10,000 years ago
• Extinction of large mammals and birds
• Smaller mammals and animals tended to
survive, population the world today as we
know it.
Are Humans at Fault?
Yes. How?
1.Hunting or harvesting
-Commercial purposes, sport, destroyed
because they are a pest
Ex- Ivory from elephants, rhino horns
2. Disrupting, fragmenting, or eliminating
habitats
Ex- Farming
3. Introducing exotic species
Ex- African honey bees led to the development
of killer bees
4. Pollution
Ex- industrial chemicals and pesticides
Species who’s status has improved
Elephant seal- dwindled to about a few
thousand animals around 1900 because of
over hunting. Presently in the hundreds of
thousands.
• Sea otter – hunted for fur reducing its
numbers to several hundred but today
numbering around 10,000
• Blue Whale – reduced to around 400 due to
whaling. Numbers are increasing but slowly.
• Bald eagle, Osprey, Peregrine falcon – all
decimated because of the use of the pesticide
DDT.
• The Endangered Species Act of 1973 has saved
many of these animals
Is abundance a problem?
• Yes. Increased confrontations
with humans.
• Sea lion populations have
increased so much their
excrement can pollute
waterways
• Mountain lion populations can
affect the safety of an area
with increased attacks.