Biology Topic 8 Llanes

Lamarck

-proposed all organisms want to become complex & perfect and change & get features enabling them easier life in their environment -thought organisms got altered organs by using their bodies in new ways and structures could change if went unused -he was wrong for many reasons: organisms don't want to be perfect, evolution doesn't necessarily improve a species or progress in a predetermined direction, & traits acquired during lifetime can't be passed on -was 1 of the 1st naturalist to suggest organisms aren't fixed & tried explaining evolution -recognized link between environment & body structure

Hardy-Weinberg Principle

5 conditions are required to maintain genetic equilibrium: the population must be very large, there can't be mutations, random mating, no movement in or out of the population, & no natural selection

HMS Beagle & Darwin

5 year journey

bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population

Species

A population whose members interbreed & produce fertile offspring

Random mating

All members of the population must have an equal opportunity to produce offspring

Bell Curve

Bell-shaped curve; individual fitness may vary from one curve end to the other & natural selection can affect the range of phenotypes and hence, the bell curve's shape

Evolution

Change in a gene pool over time.

Species vary locally

Darwin noticed that different, yet related, animal species often occupied different habitats within a local area

Why is natural variation important?

Darwin recognized that natural variation was important since it provided the raw material for evolution

Different, yet related, animal species often occupied different habitats within a local area

Depending on what's in different areas of a land mass, same/related species can vary & live in different climates; traits change in a species depending on the environment

Speciation

Formation of a new species

1809

French naturalist Jean-Baptiste Lamarck proposed a hypothesis that organisms could change during their lifetimes by selectively using/not using various body parts and suggested they could pass these acquired traits to their offspring, changing a species overtime

How does large population help maintain genetic equilibrium?

Genetic drift won't work well on a large population

Darwin and Adaptation

He proposed that over many generations, adaptation could cause a successful species to evolve into new species and that living species are descended, with modification, from common ancestors

When did Darwin grow up?

In a time when science was changing - from creationism to geologists starting to suggest Earth was really old and biologists suggesting evolution

How did speciation in the Galapagos finches occur?

It occurred by the founding of a new population, geographic isolation, changes in the new population's gene pool, behavioral isolation, and ecological competition

Fossils

Preserved remains or traces of ancient organisms; Darwin also collected these

Shuffling of genes

Shuffling of genes during sexual reproduction makes many different gene combos, but doesn't alter the relative frequency of alleles

Different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe.

Similar animals lived in similar climates; Darwin observed emus, rheas, and ostriches - looked like each other & lived in different areas with similar environments

Explanation of the speciation of Galapagos finches

South American finches arrived on the Galapagos islands and their genes may have differed from other finches due to the Founder affect. Populations on each island adapted to local environments over time & natural selection could have caused 2 distinct populations to evolve. Birds most different from each other have the highest fitness & more specialized birds have less competition for food. Overtime, species evolve in a way that increases the difference between them & a new species may evolve

Darwin noticed 3 things

Species vary globally, species vary locally, & species vary over time

What did the Grants document?

That natural selection takes place frequently - sometimes rapidly - and their work shows that variation in a species increases its likelihood to adapt & survive environmental change

When is a population in genetic equilibrium?

When allele frequencies don't change; if allele frequencies don't change, the population won't evolve.

How can mutations affect genetic equilibrium?

When mutations occur, new alleles are introduced to the gene pool and allele frequencies change.

Adaptation

any heritable characteristic that increases an organism's ability to survive & reproduce in its environment

Charles Darwin

born in England in 1809, a time when science's view of the natural world was changing from creationism to thoughts of evolution; he developed a theory of biological evolution and was invited to sail on the HMS Beagle, planning to collect many plants & animals

meiosis and fertilization don't

change relative frequency of alleles in a population

3 ways polygenic traits can affect phenotype distribution with natural selection

directional selection, stabilizing selection, or disruptive selection

descent with modification

each living species has descended, with changes, from other species over time

To keep genetic equilibrium, all genotypes in a population must?

have equal probabilities of surviving and reproducing

Where does natural selection occur?

in any situation where more individuals are born than can survive (struggle for existence), there's natural heritable variation (variation & adaptation), and there's variable individual fitness (survival of the fittest)

No movement in or out of population

individuals joining a population may introduce new alleles to the gene pool and individuals leaving may remove alleles from the gene pool

different but ecologically similar organisms

inhabited separated, but ecologically similar habitats around the globe

Artificial Selection

nature provides the variations and humans select those they find useful

Founder Effect

occurs when allele frequencies change as a result of the migration of a small subgroup of a population; they founded a different area so genes changes

Different, yet related, animal species

often occupied different habitats within a local area

common descent

principle that all living things were derived from common ancestors

Evolution

process of change over time

Genetic drift

random change in allele frequencies that occurs in small populations when an allele becomes more or less common simply by chance

Well-adapted species

survive over time

What 2 testable assumptions did Darwin's hypothesis lie on?

that there must be enough heritable variation in beak size & shape traits to provide raw material for natural selection and differences in the traits must cause differences in fitness

Darwin hypothesized that

the Galapagos finches descended from a common ancestor

Survival of the fittest

the difference in rates of survival & reproduction; survival means reproducing & passing adaptations onto the next generation in evolutionary terms

Natural Selection

the process by which organisms with variations most suited to their local environment survive and leave more offspring; acts only on inherited traits

What did beak size of the Galapagos finches relate to?

their chance of surviving drought

If natural selection acts on single gene traits,

there are changes in allele frequency leading to change in phenotype frequencies or evolution

When populations become reproductively isolated, what happens?

they can evolve into 2 separate species and this isolation can develop in many ways like behavioral, geographic, & temporal isolation

single-gene trait

trait controlled by one gene that has two alleles

polygenic traits

traits controlled by two or more genes; have a range of phenotypes that often form a bell curve