10 25-11

EVOLUTION REVIEW

Quick Review….

• What is adaptation?

• What is natural selection?

• What are the 5 steps of evolution?

• What is convergent evolution and how does it relate to analogous structures?

• What are the three structures discussed in comparative anatomy?

Natural Selection in Depth

• SC.912.L.15.13 Describe the conditions required for natural selection, including: overproduction of offspring, inherited variation, and the struggle to survive, which result in differential reproductive success.

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

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.)

• Remember the term “population capacity”

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?

CFU

• Why is important to have inherited, genetic variation?

• What are some factors of life that contribute to the “struggle to survive”

• Natural selection is an adaptation that helps a species survive and WHAT?!

• Explain population capacity• Define being evolutionary fit

BIODIVERSITY

• SC.912.L.15.3 Describe how biological diversity is increased by the origin of new species and how it is decreased by the natural process of extinction.

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 (ex. Dodo Bird, Rats, Mongoose)– 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

• The Dodo lived on the island Mauritius and was made extinct by invasive dogs, pigs, rats, etc. as well as some initial human hunting.

• Mongoose were purposefully introduced to Hawaii to deal with the rat problem (also an invasive species)… but now, due to differences in their sleeping patterns, they both live there!

• #4 Over hunting-fishing-poaching (ex. Passenger Pigeon, Tasmanian Tiger/Wolf)

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.unstable.

• StableStable ecosystems are more flexible and can rebound from natural disturbances and disasters.

• Unstable ecosystems are susceptible Unstable ecosystems are susceptible to total collapse! This would lead to to total collapse! This would lead to mass extinctions!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 – Chances are it will not come back the same – Why not?

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– Endangered: species that are in immediate

danger of becoming extinct– Threatened: species in danger of

becoming endangered in the near future

WE CAN DO SOMETHING!

• There is at least one issue that you and I can do something about preserving biological diversity…