Biology Test 5 (Chapters 13-14)

Front 1

theory:

Back 1

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.

Front 2

Strata

Back 2

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

Front 3

Paleontologists

Back 3

A scientist who studies fossils.

Front 4

fossil record:

Back 4

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

Front 5

Homology

Back 5

Similarity in characters resulting from a shared ancestry

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Homologous structures

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Structures in different species that are similar because of common ancestry.

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vestigial structures:

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

Front 8

evolutionary tree:

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A branching diagram that reflects a hypothesis about evolutionary relationships among groups of organisms.

Front 9

artificial selection

Back 9

The selective breeding of domesticated plants and animals to promote the occurance of desirable traits.

Front 10

It is important to emphasize three key points about evolution by natural selection.

Back 10

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.

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There are 2 important points to make about natural selection

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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.

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Fresh assortments of existing alleles arise every generation from three random components of sexual reproduction:

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1. crossing over,

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

3. random fertilization.

Front 13

population:

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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.

Front 14

gene pool:

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

Front 15

Micro-evolution:

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

Front 16

Hardy-Weinberg principle:

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The principle that frequencies of alleles and genotype in a population remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.

Front 17

For a population to be in Hardy-Weinberg equilibrium, it must satisfy five main conditions:

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1. There must be a very large population

2. no gene flow between populations

3. no mutations

4. random mating

5. no natural selection.

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1: The three main causes of evolutionary change:

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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.

Front 19

2: The three main causes of evolutionary change:

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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.

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3: The three main causes of evolutionary change:

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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.

Front 21

bottleneck effect:

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

Front 22

founder effect:

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Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool is not reflective of that of the original population.

Front 23

Sexual selection:

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

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sexual dimorphism:

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Marked differences between the secondary sex characteristics of males and females.

Front 25

intrasexual selection:

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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.

Front 26

The evolution of organisms is constrained:

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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.

Front 27

Microevolution:

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

Front 28

Speciation:

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

Front 29

The biological species concept defines a species as a.....

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

Front 30

Reproductive isolation:

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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.

Front 31

The morphological species concept classifies organism based on...

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

Front 32

The ecological species concept defines a species by its.....

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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.

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The phylogenetic species concept defines a species as...

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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.

Front 34

Reproductive barriers serve to...

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isolate the gene pools of species and prevent interbreeding.

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prezygotic reproductive barrier:

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Prevents mating or fertilization between species

Front 36

postzygotic reproductive barrier:

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Keep hybrids from passing on their genes.

Front 37

Five types of prezygotic barriers:

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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.

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Three types of postzygotic barriers:

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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.

Front 39

in allopatric speciation, the...

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

Front 40

list the 3 geologic processes that can isolate populations

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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.

Front 41

How do reproductive barriers arise?

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

Front 42

Sympatric speciation occurs when...

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

Front 43

How can reproductive isolation develop when members of sympatric populations remain in contact with each other?

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

Front 44

The Galapagos Islands currently have 14 species of closely related finches, called Darwins finches. These birds....

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

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Breeding males of Pundamilia nyererei have...

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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.

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Breeding males of Pundamilia Pundamilia are...

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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.

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hybrid zones are...

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

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adaptive radiation:

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the evolution of many diverse species from a common ancestor.

Front 49

When hybrid offspring are less fit than members of both parent species, we might expect....

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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).

Front 50

There are two models for the tempo of speciation, they are...

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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.

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The time interval between speciation events varies from...

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a few thousand years to tens of millions of years.

Front 52

Molecular Biology:

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

Front 53

Stabilizing Selection:

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Natural selection that prefers intermediate variants by acting against extreme phenotypes.

Front 54

Directional Selection:

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Natural selection in which individuals at one end of the phenotypic range survive and reproduce more successfully than do other individuals.

Front 55

Balancing Selection occurs when..

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natural selection maintains stable frequencies of two or more phenotypic forms in a population.

Front 56

Heterozygote Selection:

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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.

Front 57

Frequency-Dependent Selection:

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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.

Front 58

Polyploid Species:

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

Front 59

What was Darwin's phrase for evolution? What does it mean?

Back 59

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

Front 60

What anatomical feature did scientists predict in fossils of species transitioning between terrestrial and aquatic mammals?

Back 60

Reduced hind limbs and pelvic bones

Front 61

What is homology? How does the concept of homology relate to molecular biology?

Back 61

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.

Front 62

In what sense is natural selection more an editing process than a creative process?

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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.

Front 63

What is the ultimate (original) source of genetic variation? What is the source of most genetic variation in a population that reproduces sexually?

Back 63

Mutation; unique combinations of alleles resulting from sexual reproduction.

Front 64

Which is least likely to alter allele and genotype frequencies in few generations of a large, sexually reproducing population: gene flow, mutation, or natural selection? Explain.

Back 64

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

Front 65

Humans owe much of their physical versatility and athleticism to their flexible limbs and joints. But we are prone to sprains, torn ligaments, and dislocations. Why?

Back 65

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

Front 66

How does microevoluton differ from speciation?

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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.

Front 67

Which species concept could you apply to both asexual and sexual species? Explain.

Back 67

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

Front 68

Why are errors in mitosis or meiosis a necessary part of speciation by hybridization between two species?

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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

Front 69

Why was it important for researchers to establish that cichlid color sensitivity is heritable?

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

Front 70

Why might hybrid zones be called "natural laboratories" in which to study speciation?

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

Front 71

How does the punctuated equilibrium model account for the relative rarity of transitional fossils linking newer species to older species?

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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.