Evolution Flashcards Preview

AP® Biology > Evolution > Flashcards

Flashcards in Evolution Deck (74)
Loading flashcards...
1
Q

Define:

Evolution

A

Evolution is the change in frequency of a population’s inherited traits over subsequent generations.

Evolution only occurs within populations; individual organisms do not change genetically over time to adjust to their environment.

2
Q

What is the difference between microevolution and macroevolution?

A

Microevolution relates to evolutionary changes that occur within a single population. Its scope is fairly small, since it only deals with one species at a time.

Macroevolution relates to larger-scale changes and interactions between multiple populations (and thus multiple species).

3
Q

Jean-Baptiste Lamarck, a French naturalist, proposed two key ideas as part of his explanation for evolution. Name these ideas.

A

Use and disuse and inheritance of acquired characteristics

Use and disuse is the idea that we “build up” body parts that we use often, while those parts that we do not use tend to atrophy (weaken). This idea is still considered to be accurate today. In contrast, inheritance of acquired characteristics (or the thought that organisms pass down traits gained over their lifetimes) is now considered to be wrong.

4
Q

In his famous theory, Jean-Baptiste Lamarck proposed that the “use or disuse” of a trait dictated its heritability. In a classic example, giraffes who often stretched their necks would have offspring with longer necks than average. Describe the problem with this hypothesis.

A

Non-genetic traits that are acquired during an organism’s lifetime cannot be passed down to its offspring.

According to the “use and disuse” concept, organisms lose traits they do not need and develop traits that are useful to them. However, genes (not acquired traits) are inherited by offspring, making Lamarck’s theory an incorrect, and now discredited, explanation for evolution.

5
Q

Our modern understanding of evolution stems largely from the findings of which individual, who proposed the concept of natural selection?

A

Charles Darwin

Charles Darwin was a naturalist whose most famous work, On the Origin of Species, proposed the concepts that we understand to be largely true today - most notably, that natural selection drives evolutionary changes within a species as well as the development of new species.

6
Q

Define:

Natural selection

A

Natural selection is the change in frequency of a trait within a population, based on the effect that trait has on reproductive success.

Traits that allow an organism to produce more viable offspring are more likely to be passed on to future generations.

7
Q

Name five sources or fields of study that provide support for the concept of evolution.

A

The five fields of study typically considered to provide the most support for evolution are:

  • The study of the fossil record (paleontology)
  • The study of the distribution of animals and plants (biogeography)
  • Comparative anatomy
  • Comparative embryology
  • Molecular biology
8
Q

Comparative anatomy most notably includes the study of which two types of anatomical structures?

A

Homologous structures and analogous structures

9
Q

Define:

Homologous structures

A

Homologous structures are anatomical features of two species that developed from the same part of a common ancestor.

Species that possess homologous structures must be related. However, the modern versions of these structures do not have to be used for the same purpose.

10
Q

Define:

Analogous structures

A

Analogous structures are anatomical structures of two species that share a form or function, but did not develop from a common ancestor.

Species that possess analogous structures must be relatively unrelated. However, since their structures are similar in appearance or function, they may be mistaken for related species.

11
Q

As mammals, both humans and whales developed from a common ancestor. What term describes the relationship between a human arm and a whale fin?

A

Human arms and whale fins are homologous structures.

Though used for very different purposes, the appendages are evolutionarily related; both derived from a similar structure in a common ancestor.

12
Q

Birds and insects evolved independently from very different ancestors. What term describes the relationship between a bird wing and a bee wing?

A

Bird wings and bee wings are analogous structures.

Since both structures serve a similar purpose, it can be tempting to think that they are related. However, since they developed independently from features of different ancestors, they are analogous.

13
Q

What benefit does a vestigial structure give a modern organism?

A

Vestigial structures provide little to no benefit to the organisms who possess them.

While these features were likely useful to ancestral organisms, they have evolved to lose most or all of their function.

14
Q

Evolutionary biologists would classify the human appendix as which kind of structure?

A

The appendix is generally classified as vestigial.

The appendix, an outcropping of the large intestine, has long been thought to provide no function to modern humans. Though recent research has challenged this idea, for the AP Biology exam, continue to remember the appendix as a classic example of a vestigial structure.

15
Q

What is the difference between ontogeny and phylogeny?

A

Ontogeny refers to the development of an individual organism throughout its life. Phylogeny describes the evolutionary history of a species or other set of organisms.

For example, human ontogeny relates to the transition from zygote to embryo to fetus, then adult. Human phylogeny deals with the descent of modern humans from early ancestors.

16
Q

Is the development of a fertilized egg into an adult chicken an example of ontogeny or phylogeny?

A

The development of an individual chicken is ontogeny.

Ontogeny refers to an organism’s development over its lifetime, while phylogeny refers to a species’s development over evolutionary time.

17
Q

What qualities are exhibited by an organism with high fitness?

A

Organisms with high fitness are those that successfully produce a relatively large number of offspring. In general, fitness refers to the likelihood that an animal will pass down its genetic material.

On the AP Biology exam, remember that fitness is determined by reproductive success alone. A stronger, more physically capable animal that cannot reproduce is less fit than a weaker animal that can reproduce.

18
Q

Which of the following is the least evolutionarily fit?

  • A fish with underdeveloped fins
  • A fish without functioning sex organs
  • A fish without functioning eyes
A

The fish that lacks functional sex organs is the least fit.

Evolutionary fitness refers only to the ability to pass on genetic material. The other two fish certainly may have difficulty surviving, but they can still reproduce.

19
Q

Members of a population who possess beneficial traits survive long enough to produce offspring, while members with harmful traits often die before reaching sexual maturity. Which evolutionary term describes this tendency?

A

Differential reproduction describes this variation in reproductive success.

This concept is a key component of natural selection. Through this mechanism, traits that affect survival are inherited differently, regardless of whether they directly relate to reproduction.

20
Q

What term refers to the set of all genes present in a population?

A

The gene pool

A diverse gene pool allows a species to more easily adapt to changes in its environment. This quality is referred to as genetic variation.

21
Q

Define:

Genetic leakage

A

Leakage is the gene flow from one species to the gene pool of another.

22
Q

What genetic value changes within a population as evolution occurs?

A

Evolution changes a population’s allele frequency.

Alleles are different forms of genes, and evolution is a change in the frequency of genetic material. Thus, evolution causes some alleles to become more prevalent while others become more rare.

23
Q

What measurement determines the evolutionary success of an allele?

A

Evolutionary success is determined by the percent representation of an allele in the following generation.

If an allele becomes more prevalent in the gene pool, it is considered evolutionarily successful. However, factors other than natural selection can affect allele frequencies.

24
Q

Which of the following must increase in future generations for an allele to be evolutionarily successful?

  • Its phenotypic ratio
  • Its genotypic ratio
  • Both its phenotypic ratio and its genotypic ratio
A

Genotypic ratio must increase.

Technically, evolutionary success of an allele refers only to an increase in its frequency in the gene pool. Allele frequencies cannot change without altering genotype frequencies. Note that phenotype frequencies are likely to change as well, but this is not a necessary measure of success.

25
Q

Name three events or mechanisms that increase a population’s genetic diversity.

A

Many mechanisms serve to increase genetic diversity. Three of the most prevalent are:

  • Mutation
  • Migration between populations
  • Sexual reproduction, especially homologous recombination (crossing over)
26
Q

What condition must be met for a group of individuals to be considered part of the same species?

A

They must be able to breed and produce viable, fertile offspring.

A species is the most specific category in which an organism can be classified.

27
Q

Horses and donkeys can mate and produce healthy offspring called mules. Why are horses and donkeys considered separate species?

A

Mules are sterile.

Within a species, the offspring of a breeding pair must be fertile as well as viable. Since mules cannot produce offspring, this condition is not met.

28
Q

Define:

Speciation

A

Speciation is the development of new species through evolution.

Generally, speciation occurs when groups of a single species undergo divergent evolution.

29
Q

What is the difference between allopatric and sympatric speciation?

A

Allopatric speciation occurs when populations of the same species become physically isolated, usually by a geographical barrier. Over time, the populations evolve to become separate species.

Sympatric speciation refers to the formation of new species without a geographical barrier. This form of speciation can occur in cases of polyploidy in plants, where some members of a population develop an extra set of chromosomes and can no longer mate with the non-polyploid organisms. Gradually, the polyploid and non-polyploid plants separate into distinct species.

30
Q

What is the difference between adaptation and specialization?

A

Adaptation is the process of evolving a trait, through natural selection, that allows a species to better survive in its environment.

Specialization is a type of adaptation in which a species evolves to fill a specific niche.

31
Q

Viceroy butterflies mimic the appearance of monarch butterflies to repel predators. Is the evolution of this trait an example of adaptation or specialization?

A

This trait is an adaptation, not a specialization.

Through natural selection, this mimicry has evolved to increase survival. However, sharing the appearance of monarch butterflies does not fill a unique niche.

32
Q

Define:

Ecological niche

A

An ecological niche is the way a species responds to the environment it lives in, usually by filling a unique role.

A species’ niche can include its method of obtaining resources, its competitive advantages, or its relationship with predators.

33
Q

What will occur between two different species of ant that occupy the same niche?

A

They will compete with each other for resources, such as food, water, and space.

Competition occurs because resources exist in a finite amount in a given environment. In the long term, a species can avoid competition by adapting to fill a different niche.

34
Q

How does intraspecies competition affect population growth?

A

Population growth slows in response to competition.

Members of the same species fill the same niche, so they compete with each other for resources. When resources are scarce, the environment cannot support more members of the population and growth is limited.

35
Q

Define:

Inbreeding

A

Inbreeding is the production of offspring from the mating of closely related individuals.

Human examples of inbreeding include some royal families in which cousins married each other for many generations.

36
Q

Define:

Outbreeding

A

Outbreeding is the introduction of new genetic material through mating with unrelated individuals.

Many purebred species, such as dogs and cattle, have developed predispositions for genetic diseases as a result of inbreeding. When the diversity of the gene pool is increased, offspring are more likely to be healthy.

37
Q

A small group of people from Indiana decide to start a new society on a deserted island. Several rare genetic diseases happen to be over-represented in this group, so their offspring display high frequencies of these diseases as well, as do their offspring. This best relates to what phenomenon?

A

The founder effect

This phenomenon is a form of genetic drift in which a small group of individuals breaks off from a larger population. Alleles that happen to be prevalent in this group will now be displayed much more frequently in future generations than would be expected in the original, larger population.

38
Q

What term describes a major reduction in the number of individuals in a population?

A

A significant reduction in population size is called a bottleneck.

Bottlenecks are generally caused by catastrophic events, whether environmental (such as a natural disaster) or human-related.

39
Q

At one point, overhunting caused the American bison population to drop to fewer than 1000 individuals. What term describes this situation?

A

In this example, the bison population experienced a bottleneck.

Bottlenecks can dramatically change the gene pool, since all subsequent members of the species descend from a small number of individuals.

40
Q

What is genetic drift?

A

Genetic drift describes changes in allele frequencies that result from random events.

Often, genetic drift involves situations where part of the population experiences some disaster or becomes isolated from the rest. For example, consider a rat population where allele freqencies for coat color are fairly even. If a flood happens to kill most of the white rats, the resulting decrease in the “white” allele is a result of genetic drift.

41
Q

What kind of factors promote genetic drift?

A

Genetic drift is promoted by random chance. It relates to changes in allele frequency that occur separately from natural selection.

One example is a bottleneck, or a sharp reduction in population size. The gene pool of the individuals who happen to survive will then determine the characteristics of their offspring, regardless of whether these traits are favorable.

42
Q

What occurs when two groups undergo divergent evolution?

A

Divergent evolution causes related groups to become increasingly different. In other words, they evolve apart.

Over time, divergent evolution can lead to speciation, when groups differ to the point of being unable to interbreed.

43
Q

What occurs when two groups undergo parallel evolution?

A

Parallel evolution causes distinct lineages to evolve similar traits over time.

This differs from convergent evolution, in which two lineages become increasingly more similar to each other. In contrast, parallel evolution involves the independent development of like traits in organisms without an increase in overall resemblance.

44
Q

What occurs when two groups undergo convergent evolution?

A

Convergent evolution causes unrelated, originally dissimilar groups to become increasingly similar.

This often occurs when two species begin to fill the same ecological niche.

45
Q

What type of evolution is demonstrated by bats and owls?

A

Bats and owls developed through convergent evolution.

While both possess the ability to fly, bats are mammals while birds are avian species. Their anatomical structures did not come from a common ancestor, but developed separately and became more similar over time.

46
Q

Which type of evolution can result in the existence of homologous structures?

A

Divergent evolution

By definition, homologous structures must have developed from a common ancestor. Thus, species with these structures are the eventual result of divergence from that ancestor.

47
Q

Which type of evolution can result in the existence of analogous structures?

A

Convergent evolution

When two unrelated species converge, they often evolve features with similar appearances or functions. Since these structures did not develop from a common ancestor, they are analogous.

48
Q

Name the three types of natural selection.

A

Natural selection can either be directional, stabilizing, or disruptive.

49
Q

Which type of natural selection is shown in the image below?

A

Stabilizing selection

Stabilizing selection occurs when extreme phenotypes confer a disadvantage to an organism’s fitness. Over time, the frequency of moderate phenotypes will increase.

50
Q

Which type of natural selection is shown in the image below?

A

Disruptive selection

Disruptive selection occurs when extreme traits are advantageous while moderate traits are not. As a result, the frequencies of the extreme phenotypes increase over time.

51
Q

Which type of natural selection is shown in the image below?

A

Directional selection

Directional selection occurs when a single extreme trait provides a survival advantage. Over time, the frequency of individuals with that trait will rise.

52
Q

Which type of selection helps determine human birthweight?

A

Birthweight is influenced by stabilizing selection.

A baby born too small would have difficulty surviving on its own, but an abnormally large baby would be hard for the mother to deliver. Since birthweight is kept within a moderate range, it exemplifies stabilizing selection.

53
Q

A population of horses consists of many individuals with very long manes and many with short manes, but few in the middle. This is likely the result of which form of natural selection?

A

This population exemplifies disruptive selection.

Disruptive selection favors extreme variations of a trait over more moderate ones. A classic example is the London peppered moth, where black wings were easily camouflaged in industrial surroundings and white wings blended in within rural areas. Gray moths, which could be seen by predators in both areas, became less prevalent over time.

54
Q

Which type of selection best relates to antibiotic-resistant bacteria?

A

Antibiotic resistance is an example of directional selection.

Before selection, a bacterial colony contains members with varying degrees of resistance. After exposure to an antibiotic, only those individuals with high resistance remain, and they can propagate to form a new, resistant colony.

55
Q

Define:

Group selection

A

Group selection refers to genetic changes that occur over time due to the fitness of a group rather than an individual.

Group selection has been used to explain altruism, or selfless behavior. Though it remains controversial among evolutionary biologists, this topic could certainly be mentioned on the AP Biology exam.

56
Q

What term is often used to connect group selection to altruistic behavior?

A

Kin selection, or the evolutionary preference for behaviors that benefit relatives, is often used to explain altruism.

Not all species exhibit altruistic behavior. Within those that do, “selfless” actions that can harm an individual often benefit the surrounding members of the population. This indirectly passes on the genes of that individual by promoting the survival and reproduction of family members.

57
Q

With regard to evolution, what is an isolating mechanism?

A

An isolating mechanism is a feature that prevents two species from mating or producing fertile offspring. Such features prevent distinct species from combining.

Isolating mechanisms can be either prezygotic or postzygotic.

58
Q

What is the difference between prezygotic and postzygotic isolating mechanisms?

A

Prezygotic mechanisms prevent two species from mating. Postzygotic mechanisms allow mating but prevent the development of viable, fertile offspring.

If these terms are unfamiliar, their names can give away their meaning. “Prezygotic” relates to events before zygote formation, while “postzygotic” relates to events that occur afterward.

59
Q

What is hybrid inviability?

A

In cases of hybrid inviability, mating can occur and form a hybrid offspring, but that offspring will not develop into a healthy adult.

Hybrid inviability is an example of a postzygotic barrier between distinct species.

60
Q

What is hybrid breakdown?

A

In cases of hybrid breakdown, mating can occur and form healthy, fertile hybrid offspring. However, later hybrid generations (F2 and onward) are unhealthy and sometimes cannot reproduce themselves.

Hybrid breakdown is the final post-zygotic barrier that separates distinct species.

61
Q

What is hybrid sterility?

A

In cases of hybrid sterility, mating can occur and form a healthy hybrid offspring. However, the hybrid is sterile and cannot reproduce.

Mules are examples of hybrid sterility, which is a postzygotic barrier between distinct species.

62
Q

One species of moth mates in the fall, while a nearby species of moth only mates in the spring. Which mechanism keeps these two species distinct?

A

Temporal isolation, a type of prezygotic isolation, separates these two species.

Temporal isolation usually relates to differences in mating seasons or times, though it can also separate nocturnal from diurnal species.

63
Q

One species of fish mate with another to produce viable offspring. When these offspring interbreed, their progeny are viable but sterile. Which mechanism keeps these two species distinct?

A

Hybrid breakdown, a type of postyzygotic isolation, separates these two species.

Hybrid breakdown relates to a decrease in viability within progressive generations of hybrids.

64
Q

In a hypothetical situation, allele frequencies in a population remain unchanged over multiple generations. Though this condition does not occur naturally, it is often used as the basis for mathematical models. What term describes this situation?

A

This situation is called Hardy-Weinberg equilibrium.

65
Q

Name the five prerequisites for Hardy-Weinberg equilibrium.

A

Hardy-Weinberg equilibrium requires five conditions:

  1. Large population size
  2. No mutation
  3. No inward or outward migration
  4. No natural selection
  5. Random mating
66
Q

A very large, mutation-free population of finches is entirely isolated within their geographic area. Males tend to grow bright feathers to attract potential mates. What condition(s) of Hardy-Weinberg equilibrium does this population violate?

A

This population violates the condition of random mating.

A large population size, lack of mutation, and lack of migration all fit Hardy-Weinberg criteria. However, if mates are chosen based on certain characteristics, mating is not random and equilibrium is violated.

67
Q

What two equations can be used when a population is assumed to be in Hardy-Weinberg equilibrium?

A

The main Hardy-Weinberg equation is p2 + 2pq + q2 = 1. Since this statement assumes that only two alleles are present, and these alleles are represented by “p” and “q,” p + q = 1 is also relevant.

For these equations to hold true, the proportion of each allele must be described in decimal form. For example, if the A allele comprises 36% of the gene pool, its frequency would be 0.36.

68
Q

In the Hardy-Weinberg equation, what variable or expression refers to the frequency of the dominant allele in the gene pool?

A

p

When dealing with Hardy-Weinberg, remember that alleles are denoted by single letters. Conventionally, the dominant allele is “p” and the recessive allele is “q.”

69
Q

In the Hardy-Weinberg equation, what variable or expression refers to the frequency of the heterozygous genotype in the gene pool?

A

2pq

Remember that genotypes in the Hardy-Weinberg equation are denoted by expressions, not single letters. p2 represents the proportion of homozygous dominant individuals, while q2 represents the frequency of the homozygous recessive genotype.

70
Q

A and a are the only two alleles that exist for a certain trait. In a stable population, 9% of individuals have the aa genotype. What percentage of individuals are heterozygous?

A

42%

The frequency of the homozygous recessive genotype, q2, is 0.09. From this information, it can be found that q = 0.3. Since p + q = 1, p must be equal to 0.7. The heterozygote frequency, 2pq, is thus (2)(0.7)(0.3) or 0.42.

71
Q

How are genetic differences between two species used to quantify their evolutionary relationship?

A

Random mutations occur at a predictable rate. Thus, the differences between the genetic sequences of two species can be used to estimate the time since they diverged from a common ancestor.

Natural selection can increase the rate at which a certain mutation predominates, so this measurement is only an estimate.

72
Q

Which theory states that evolution occurs in short, rapid bursts within long periods of little change?

A

The Punctuated Equilibrium Theory

According to this theory, a species will usually exist in a static state where virtually no evolutionary change occurs. This state is interrupted by brief periods of evolution that are prompted by specific events.

73
Q

The Miller-Urey experiment used water, methane, ammonia, and hydrogen gas to simulate the conditions of early Earth. What molecules were produced by this experiment?

A

Amino acids were produced.

This result, along with those of similar experiments, implied that organic biomolecules could be synthesized from inorganic substances. This was a major breakthrough in the study of the origin of life.

74
Q

What biochemical evidence supports the idea that all life descends from a common ancestor?

A

All living organisms encode their genetic material as DNA. They also share the genetic code by which this material is converted into protein.

Specifically, DNA is transcribed into RNA, which is translated into protein.