lecture 4: evolution by natural selection Flashcards
What 4 patterns are explained by evolution by natural selection?
- Species are diverse, but there is an unity.
- Species are adapted to their environments.
- Similar species are found relatively near to each other.
- Species are not perfect.
Who is behind the concept of evolution by natural selection?
Darwin and Wallace
What are Darwin and Wallace’s two claims?
- Evolution has occurred; species change through time.
2. Mechanism of evolution = natural selection
What is special creation (2 elements) ?
- Species were created independently by God.
2. Species were unchangeable and had been unchanged since the moment of their creation.
(1) What is typological thinking? (Plato)
Types are created and immutable.
(2) What is Aristotle’s scale of nature?
Types can be ranked higher/lower based on complexity.
(3) What was Lamarck’s thinking (2 elements)?
Species change through time from low to high (scale of nature); INVIDUALS EVOLVE.
- Individuals change in response to environment depending if of use/disuse of certain traits.
- Pass on acquired characteristics to their offspring.
(4) What was Darwin and Wallace’s thinking?
Species change through time and are related via a common ancestor (tree-thinking); POPULATIONS EVOLVE (variations within populations).
What are the two components of Darwin’s Theory of Evolution?
- Decent with Modification
2. Natural Selection
What is “fitness”?
The ability to survive and reproduce offsprings who can survive and reproduce too.
What is “adaptation”?
Any traits that increase fitness.
What are Darwin’s 4 observations?
- Competition among individuals in a population to survive and reproduce.
- Variation in traits exists in population.
- Certain traits give individuals a survival/reproductive advantage.
- Many traits are heritable (can be passed on to offspring).
What are Darwin’s 2 conclusions?
- Individuals with advantageous trait are more likely to survive and reproduce.
- Over time, more individuals in the population will have the advantageous trait.
What is natural selection?
Individuals with certain traits produce more offspring that survive than do individuals without those traits. Selected traits increase in frequency in the population, from one generation to the next, causing evolution.
Evolution by natural selection occurs when…
Heritable variation lead to differential success in survival and reproduction.
What is selection pressure?
When nature puts pressure on the survival and reproduction of individuals in a population. Selection pressures vary from one environment to another OR in the same environment throughout time.
Where can selection pressure come from?
- Physical environment: climate, availability of ressources
2. Interactions with another species: competition, mutalism, predator/prey, parasite/host
What is Decent with Modification (2 claims)?
- Species change through time.
2. Species are related by common ancestry.
What evidence support that “species change through time”? (2 elements)
- Fossil record
2. Vestigial traits
What does fossils show?
- Traces of organisms that lived in the past; life is ancient
- Proof for extinct species
- Extinct species & extant species with similar traits share same geographic location
- Transitional features (“missing link”) show evolution of species
What are vestigial traits?
Trait that is incompletely developed with no/reduced function, but is similar to a more developed, functioning trait in closely related species
EX: tail & human’s coccyx
What is a homology?
A similarity between species that evolved from a common ancestor.
What is biogeography?
Study of geographical distribution of organisms today and over time. Reveals that similar species are linked by geography.
What are the biogeographic relationships?
Similar species (extinct or extant) involved from a common ancestor inhabitates same area.
What is an analogy?
Similarity not due to a common ancestor.
What is convergent evolution?
Organisms with separate ancestors may show simlar adaptations due to similar selection pressures all around the world. It produces ANALOGIES.
Why are adaptations limited (4 elements)?
- Fitness trade-offs: cannot maximize one trait without negatively affecting another
- Genetic constraints: gene pool in population is limited
- Historical constraints: some adaptations are built from exaptations (ancient adaptation that does not serve same purpose anymore)
- Environmental constraints: envrionments change and idea of “perfection” changes too
