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EVOLUTION
Darwin's Theory of Evolution
• Traveled all over world and made observations, he then concluded the following– Organisms have ability to overproduce– Inherited variation exist-arise from
mutation, genetic recombination and random fertilization
– Limited resources(i.e food, habitat) limit carrying capacity of species-leads to survival of the fittest
• What is adaptation?– When change in phenotype increases
animals success of reproduction
What is the difference between artificial and natural selection?
Artificial Selection
• Cattle and Livestock • Ranchers usually only breed their best
cattle…. Why?
Natural Selection
• What is natural selection?–When an adaptation/characteristic
allows one organism to survive and reproduce better than others
–Survival of the Fittest!!!!!• The struggle to survive results in one organism
“besting” another in the competition for resources
What’s required for natural selection?
• REPRODUCTION!!!• Overproduction of offspring: Animals
reproduce to create more offspring than will likely survive (ex. Insects, birds, mice, fish, frogs, etc. etc.)– Sea stars produce over 1 million eggs each
season
Struggle to Survive
• If resources were unlimited and there was no threat from predation, there would be less natural selection.
• The struggle to survive results in one organism “besting” another in the competition for resources– That takes care of the “Survival of the
Fittest”… but remember, natural selection is not just about survival…
Differential Reproductive Success
• If one organism survives extremely well but never actually reproduces, its genes will never be passed down and cannot be selected for…– Evolutionary “fitness” is the ability of an
organism to survive and reproduce… it’s all about passing on your genes…
Adaptations that aid in reproduction
• The goal of reproduction is how you end up with sometimes unusual and frivolous looking adaptations….
Inherited Variation
• There must be genetic variation in the population.
• If there is no genetic variation, then the genes coding for certain traits will always be the same.
• Genes are passed down from generation to generation, thus, we get heritable traits.
• What are some traits/characteristics that are NOT heritable?
BIOLOGICAL DIVERSITY
• First… what is it?– Biological diversity refers specifically to the
variety of organisms within a given area
• Next… why are we concerned with it?– One of the ways in which scientists
evaluate the environmental health of a region
Reduction of Diversity
• Reduction of diversity creates less opportunities for inherited variation – Why does that matter?
Biodiversity can be reduced by…
• #1 Loss of Habitat (ex. Rainforest)
• #2 Decrease in Range (ex. Western ranching)
• #3 Introduction of non-native species – Example: Zebra Mussels in Great Lakes
and Bullmeise Pytons in Everglades– This usually happens by accident, such as
stowaways in ship and aircraft cargo holds– Can be devastating– Management of this issue must be
thoroughly thought through
http://www.youtube.com/watch?v=kU6Oo1iQaOY&safety_mode=true&persist_safety_mode=1&safe=active
Genetic Diversity
• Loss of inherited variation • When a species on the brink of
extinction is preserved, reduced genetic diversity within the species is a concern– Why?
• Populations that survive extinction tend to be genetically uniform
The result…
• Genetic uniformity is detrimental – If one individual is susceptible to disease all
individuals are susceptible disease – If one individual has a weakness, they all have the
same weakness• Easy to wipe out a whole population
• High genetic variation means at least some individuals will survive changes or diseases and the species will avoid extinction
BIOLOGICAL DIVERSITY = STABILITY
• As each species goes extinct, the system becomes more unstable.
• Stable ecosystems are more flexible and can rebound from natural disturbances and disasters.
• Unstable ecosystems are susceptible to total collapse! This would lead to mass extinctions!
Once its gone its gone forever
• Mutations are the only things that increase genetic variation
• Since that evolution takes millions of years it is pretty much safe to say that once genetic diversity is gone its lost forever
So…. In Essence
• When new species evolve, biodiversity is increased.– An increase in biodiversity leads to greater
ecological stability • When a species goes extinct,
biodiversity is decreased– A decrease in biodiversity leads to
ecological INstability
Extinction• Extinction: What is it?• What’s the difference between
threatened, endangered, and extinct?– Extinct: species that no longer exist
• Example Megladon Shark– Endangered: species that are in immediate
danger of becoming extinct• Humpback Whales
– Threatened: species in danger of becoming endangered in the near future• Burrowing owl
Read Articles on Zebra Mussels and Burmese python
• Answer the following:– How did they get here?– Why are they a threat to the habitat they
invaded– Could this invasion been prevented? If so
what things could have been done?
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