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?
Cattle and Livestock
Ranchers usually only breed their best cattle…. Why?
What is natural selection?
When an adaptation/characteristic allows one organism to survive and reproduce better than others
What’s required for natural selection?
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….
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?
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
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.
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)
Loss of inherited variation
When a species on the brink of extinction is preserved, reduced genetic diversity within the species is a concern
Populations that survive extinction tend to be genetically uniform
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
Chances are it will not come back the same
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: 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…