Biology - CP 22-23

I'll do so great on this test!!!

What is speciation? How does it occur?

The development of a new species It occurs from isolation to being allopatric or sympatric or some other form.

Describe how speciation may have occurred in Darwin’s finches?

An ancestor finch was distributed among the different islands and isolated. Each population of finches had certain variations of traits that were more likely to survive and reproduce. Eventually they changed so much they could no longer interbreed.

Compare the various forms of isolation and the pattern of speciation associated with each.
Allopatric Speciation = Geographic Isolation
Sympatric Speciation = Behavioral, Temporal, Reproductive Isolation

Allopatric Speciation is when species are separated physically. That means that they are not in contact with the species and cannot mate or interact with them. Sympatric Speciation is when the species is separated behaviorally, like they interact differently. They are not blocked from them geographically.

What is the difference between prezygotic barriers and post zygotic barriers?

Prezygotic barriers- barriers that happen before an egg is fertilized. Post zygotic barriers- barriers that happen after an egg is fertilized

Be able to identify what types of isolation are present in an example of two populations no longer interbreeding.

The Juncos at UCSD and Mt. Laguna are a result of allopatric speciation. This is because they used to travel alongside each other, however now both of the groups live in different environments.

Why/how does isolation lead to speciation?

Two populations have a major decrease in gene flow between the groups- genetic variations are more beneficial in certain environments and those alleles in a population increase in frequency. The dramatic changes depending on the environment the populations are in eventually become so different from each other they are different species.

What is a species?

Organisms that can interbreed and their offspring can reproduce.

What role does the environment play in natural selection?

The environment favors certain traits in a population that are more beneficial for survival.

TRUE or FALSE: Natural Selection takes place to a population.

TRUE

TRUE or FALSE: Natural Selection takes place over the lifetime of an individual. EXPLAIN

TRUE, because over the species lifetime the environment could change that can cause the mutations a species has to be useless and/ or useful, and the environment of predators/prey that a species has available can always sway.

What could you look at to figure out if two populations are the same species?

The most common answer is physical appearance, because if they look similar then that could mean that they have a more common ancestor. If you also look at their behavior closely and how they act under stressful/uncommon situations, that could also indicate that they are more similar. But DNA is the most accurate, because you can compare the DNA to see how similar they are to each other, and that can truly indicate how related they are, even if they have different appearances.

What investigation can you do to test if two groups are the same species? Be sure to account for variables that need to be held constant. Are there any variables that you are unable to control?

We can first see if they act similarly to each other. We can't control how they will act in the test, or the way that they interact with each other, but we can put them into a controlled environment to see if that has an impact.

How are Darwin’s finches an example of adaptive radiation?

Before they came to islands as one species, however, because of the new environment change and new resources, they began to separate themselves and mutate in order to adapt to the new area.

Explain why after an environmental change a population might…
* expansion of some species
* the emergence of new distinct species as populations diverge under different conditions,
* and the decline–and sometimes the extinction–of some species.

After an environment change, if it is beneficial then the species would increase because of new resources. Those who were not made fit into the environment could have mutated because of the environment/expansion of species, therefore becoming a new species that could live in different conditions. Some species who were not made for the environment could be taken out by natural selection, or they pass off different mutations to their offspring, therefore making them another species. This can cause species to die off.***

Compare the concepts of homologous structures, analogous structures, and vestigial structures.

Homologous structures are when different species have similar functions/structures to other species. Analogous structures are when structures of different species that have similar functions, however not structures. Vestigial structures are when structures used to have a purpose, but are no longer useful.

Compare convergent evolution, divergent evolution and co evolution. Provide an example of each.

Divergent evolution is when a species with a common ancestor changes to become increasingly different over time, like a modern elephant and woolly mammoth. Convergent evolution is when unrelated species develop similar characteristics over time, the bodies of sharks and dolphins. Co evolution is when influences are made by closely associated species during evolution, like plants and their pollinators.

How can vestigial structures be used as evidence for common ancestry? Provide examples.

Because it helps trace the evolutionary origin of the species Human and apes for divergent evolution, like the body shape of dolphins and sharks.

What is a homologous chromosome?

When a set of one maternal and one paternal chromosome that pair up with each other inside a cell

What creates genetic variety from generation to generation?

Mutations that change the pattern of the DNA.

How is the amount of genetic variety present in a population related to its resilience after an environmental change? Are they more or less likely to adapt/evolve?

If a population with very little mutation goes through an environmental change, then they are less likely to adapt/evolve with different mutations because there is very little variety. The population with more genetic diversity would be more willing to adapt/evolve because they are more likely to resist any negative changes in the environment.

What is the difference between phylogenetic trees and cladograms?

Cladograms are based on characteristics, while phylogenetic trees are about genetic relationships.

What sources of evidence can be used to determine common ancestry?

The anatomy of the species, and the genetic DNA of the species, because how well the species is related to you depends on how well the DNA matches each other, and what genes/mutations the species possesses.

Are some sources of evidence more reliable than others? What is the most reliable source of evidence?

I believe that DNA matching is the most efficient when trying to identify how closely related the species is, because sometimes anatomy can be misleading as they can be a product of convergent evolution.

Are all the other juncos in North America the same species? How do we know?

Yes-they interbreed and they have similar DNA

How are the juncos in North America an example of adaptive radiation?

The Yellow eye junco spread into North America and evolved to each unique habitat .to look different from the original.