Unit Two: Evolution

Hardy-Weinberg equilibrium conditions

1) All traits are selectively neutral (no natural selection) 2) Mutations do not occur 3) The population must be isolated from other populations (no gene flow) 4) The population is large (no genetic drift) 5) Mating is random

Darwin's theory of evolution by natural selection:

1) Populations possess an enormous reproductive potential 2) Population sizes remain stable 3) Resources are limited 4) Individuals compete for survival 5) There is variation among individuals in a population 6) Much variation is inheritable 7) Only the most fit individuals survive 8) Evolution occurs as favorable traits accumulate in the population

Of the following anatomical structures, which is homologous to the bones in the wing of a bird? A) cartilage in the dorsal fin of a shark B) bones in the flipper of a whale C) chitinous struts in the wing of a butterfly D) bony rays in the tail fin of a flying fish E) bones in the hind limb of a kangaroo

B) bones in the flipper of a whale

Which of the following is true of all horizontally oriented phylogenetic trees, where time advances to the right?

The common ancestor represented by the rightmost branch point existed more recently in time than the common ancestors represented at branch points located to the left.

use and disuse

body parts of organisms can develop with increased usage, while unused parts weaken (theory proposed by Jean-Baptiste Lamarck)

analogous structures

body parts that resemble one another in different species, not because they have evolved from a common ancestor, but because they evolved independently as adaptations to their environments (ex. fins of sharks and penguins because they are adapted to swimming)

evolution

changes in populations, species, or groups of species overtime; the process by which the frequency of heritable traits in a population changes from one generation to the next

To apply parsimony to constructing a phylogenetic tree,

choose the tree that represents the fewest evolutionary changes, in either DNA sequences or morphology.

The role that humans play in artificial selection is to

choose which organisms breed, and which do not

homologous structures

describes body parts that resemble one another in different species because they have evolved from a common ancestor; structures may look different but will resemble one another in pattern (ex. hind limbs in whales and wings of flightless birds because they provide evidence of evolutionary heritage)

stabilizing selection

eliminates individuals that have extreme or unusual traits; individuals with the most common form of a trait are the best adapted

molecular biology

examines the nucleotide and amino acid sequences of DNA and proteins from different species

directional selection

favors traits that are at one extreme of a range of traits; traits at the opposite extreme are selected against

artificial selection

form of directional selection carried out by humans when they sow seeds or breed animals that possess desirable traits

sympatric speciation

formation of new species without the presence of a geographic barrier

paleontology

fossils that reveal the prehistoric existence of extinct species; changes in species and the formation of new species can be studied

Both ancestral birds and ancestral mammals share a common ancestor that was terrestrial. Today, penguins (which are birds) and seals (which are mammals) have forelimbs adapted for swimming. What term best describes the relationship of the bones in the forelimbs of penguins and seals, and what term best describes the flippers pf penguins and seals?

homologous; analogous

natural selection

individuals possess alleles (genotypes) that generate traits (phenotypes) that enable them to be more successful in their environment than other individuals; survival of the fittest

mutations

introduce new alleles that may provide a selective advantage or deleterious effects

Cladograms (a type of phylogenetic tree) constructed from evidence from molecular systematics are based on similarities in

mutations to similar genes

behavioral isolation

occurs when a species does not recognize another species as a mating partner

hybrid sterility

occurs when hybrids become functional adults but are reproductively sterile

hybrid breakdown

occurs when hybrids produce offspring that have reduced viability or fertility

mechanical isolation

occurs when male and female organisms are structurally incompatible

gametic isolation

occurs when male gametes do not survive in the environment of the female gamete or when female gametes do not recognize male gametes

habitat iisolation

occurs when species do not encounter one another

temporal isolation

occurs when species mate during different season/times

hybrid indviability

occurs when the zygote fails to develop properly and aborts or dies before reaching reproductive maturity

genetic drift

random increase or decrease of alleles (ex. hurricanes)

When using a cladistic approach to systematics, which of the following is considered most important for classification?

shared derived characters

embryology

similar stages in development among related species; helps establish evolutionary relationships

gene flow

the movement of individuals between populations resulting in the removal of alleles from a population when they leave or the introduction of alleles when they enter

If two modern organisms are distantly related in an evolutionary sense, then one should expect that

they should share fewer homologous structures than two more closely related organisms

divergent evolution

two or more species that originate from a common ancestor and become increasingly different overtime

parallel evolution

two related species that have made similar evolutionary changes after their divergence from a common ancestor

convergent evolution

two unrelated species that share similar traits

allopatric speciation

when a population is divided by a geographic barrier so that interbreeding between the two resulting populations is prevented

founder effect

when allele frequencies in a group of migrating individuals are, by chance, not the same as that of their population of origin

disruptive selection

when the environment favors extreme or unusual traits, while selecting against the common traits

bottleneck

when the population undergoes a dramatic decrease in size