Biology Test 5 (Chapters 13-14)

a widely accepted explanatory idea that is broader in scope than a hypothesis, generates new hypotheses, and is supported by a large body of evidence.

Rock layers formed when a new layer of sediment covers an older one and compresses it.

A scientist who studies fossils.

the chronicle of evolution over millions of years, engraved in the order of which fossils appear in rock strata.

remnants of features that served important functions in an organism's ancestors.

1. Although natural selection occurs through interactions between individual organisms and the environment, individuals do not evolve. Rather, it is the population, the group of organisms, that evolves over time.

2. Natural selection can only amplify or diminish heritable traits.

3. Evolution is not goal directed; it does not lead to perfectly adapted organisms.

1: Natural selection is more of an editing process than a creative mechanism.

2: Natural selection is contingent on time and place, favoring those heritable traits in a varying population that fit the current, local environment.

1. crossing over,

2. independent orientation of homologous chromosomes at metaphase 1 of meiosis, and

3. random fertilization.

A group of individuals of the same species, that live in the same area, and interbreed.

We can measure evolution as a change in the prevalence of certain heritable traits in a population over a span of generations.

All copies of every type of allele, at every locus, in all members of the population.

A change in the relative frequencies of alleles in a population over a number of generations and evolution occurring on its smallest scale.

1. There must be a very large population

2. no gene flow between populations

3. no mutations

4. random mating

5. no natural selection.

1. natural selection - If individuals differ in their survival and reproductive success, natural selection will alter allele frequencies.Organisms more fit to survive will pass on their genetic information.

Genetic drift - In a process called genetic drift, chance events can cause allele frequencies to fluctuate unpredictably from one generation to the next.The smaller the population, the more impact genetic drift is likely to have.

1. Gene flow - Allele frequencies in a population can also change as a result of gene flow, where a population may gain or lose alleles when fertile individuals move into or out of a population or when gametes (such as plant pollen) are transferred between populations.Gene flow tends to reduce differences between populations.

Genetic drift resulting from a drastic reduction in population size. Typically, the survivng population is no longer genetically representative of the original population.

a form of natural selection in which individuals with certain characteristics are more likely to obtain mates.

when members of the same sex (within a species) compete with each other in order to gain opportunities to mate with others, e.g. the male against male competition for females.

1.Selection can act only on existing variations. New, advantageous alleles do not arise on demand.

2. Evolution is limited by historical constraints. Evolution co-opts existing structures and adapts them to new situations.

3. Adaptations are often compromises. The same structure often performs many functions.

4. Chance, natural selection, and the environment interact. Environments often change unpredictably.

the change in the gene pool of a population from one generation to the next.

the process by which one species splits into two or more species. Each time speciation occurs, the diversity of life increases.

group of populations whose members have the potential to interbreed in nature and produce fertile offspring (offspring that themselves can reproduce).

the situation where different species may live in the same area, but properties of individuals prevent them from interbreeding. The things which stop species or groups of organisms reproducing sexually are called isolating mechanisms.

observable physical traits and can be applied to asexual organisms and fossils.

ecological niche and focuses on unique adaptations to particular roles in a biological community. For example, two species may be similar in appearance but distinguishable based on what they eat or the depth of water in which they are usually found.

the smallest group of individuals that share a common ancestor and thus form one branch of the tree of life. Biologists trace the phylogenetic history of a species by comparing its morphology, DNA sequences, or biochemical pathways.

isolate the gene pools of species and prevent interbreeding.

Prevents mating or fertilization between species

Keep hybrids from passing on their genes.

1. habitat isolation - there is a lack of opportunity for mates to encounter each other.

2. temporal isolation - there is breeding at different times or seasons.

3. behavioral isolation - there is failure to send or receive appropriate signals.

4. mechanical isolation - there is physical incompatibility of reproductive parts.

5. - gametic isolation, there is molecular incompatibility of eggs and sperm or pollen and stigma.

1. reduced hybrid viability - interaction of parental genes impairs the hybrid’s development or survival.

2. reduced hybrid fertility - hybrids are vigorous but cannot produce viable offspring.

3. hybrid breakdown - hybrids are viable and fertile, but their offspring are feeble or sterile.

initial block to gene flow may come from a geographic barrier that isolates a population.

1. A mountain range may emerge and gradually split a population of organisms that can inhabit only lowlands.

2. A large lake may subside until there are several smaller lakes, isolating certain fish populations.

3. Continents themselves can split and move apart.

The environment of an isolated population may include different food sources, different types of pollinators, and different predators.

a new species arises within the same geographic area as its parent species.

Gene flow between populations may be reduced by habitat differentiation, or sexual selection.

share many finchlike traits, differ in their feeding habits and their beaks are specialized for what they eat, and they arose through adaptive radiation.

a bright red back and dorsal fin. P. nyererei females prefer red males over blue males, the vision of P. nyererei females is more sensitive to red light than blue light. This color sensitivity is heritable.

metallic blue-gray, P. pundamilia females prefer blue males over red males. The vision of P. pundamilia females is more sensitive to blue light than red light. This color sensitivity is heritable.

regions in which members of different species meet and mate to produce at least some hybrid offspring.

the evolution of many diverse species from a common ancestor.

natural selection to strengthen, or reinforce, reproductive barriers, thus reducing the formation of unfit hybrids, and that barriers between species should be stronger where the species overlap (that is, where the species are sympatric).

1. The punctuated equilibria model draws on the fossil record, where species change most as they arise from an ancestral species and then change relatively little for the rest of their existence.

2. Gradual Pattern: Other species appear to have evolved more gradually.

a few thousand years to tens of millions of years.

The study of biological structures, functions, and heredity at a molecular level.

a type of balancing selection in which heterozygous individuals have greater reproductive success than either type of homozygote, with the result that two or more alleles for a gene are maintained in a population.

a type of balancing selection that maintains two different phenotypic forms in a population. In this case, selection acts against either phenotypic form if it becomes too common in a population.

an organism that has more than two complete sets of chromosomes as a result of accidental cell division.

Descent with modification. An ancestral species could diversify into many descendant species by the accumulation of adaptations to various environments.

Reduced hind limbs and pelvic bones

Homology is similarity in different species due to evolution from a common ancestor. Similarities in DNA sequences or proteins reflect the evolutionary relationship that is the basis of homology.

Natural selection connot create beneficial traits on demand but instead "edits" variation in a population for individuals with those traits that are best suited to the current environment.

Mutation; unique combinations of alleles resulting from sexual reproduction.

Mutation. Because mutations are rare, their effect on allele and genotype frequencies from one generation to the next is likely to be small.

Adaptations are compromises: Structural reinforcement has been compromised as agility was selected for.

Microevolution involves evolutionary changes within a population; speciation occurs when a population changes enough that it diverges from its parent species and becomes a new species.

The morphological, ecological, and phylogenetic species concepts could all be used because they do not rely on the criterion of reproductive isolation.

If a hybrid has a single copy of the chromsome from two species, homologous pairs cannot join and separate during meiosis to produce gametes. Errors in mitosis or meiosis must somehow duplicate chromosomes so that there is a diploid number of each set and normal gametes can form

Sentivity to red is the phenotypic trait that allows P. nyererei females to choose P. nyererei males as mates, ensuring reproductive isolation.

By studying the fate of hybrids over time, scientists can directly observe factors that cause (or fail to cause) reproductive isolation.

If speciation takes place in a relatively short time or in a small isolated population, the transiton of one species to another may be difficult to find in the fossil record.