Evolution

What three patterns of biodiversity did Darwin note?

-Darwin noticed that different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe. -Darwin noticed that different, yet related, animal species often occupied different habitats within a local area. -Darwin noticed that some fossils of extinct animals were similar to living species

What do homologous structures and similarities in embryonic development suggest about the process of evolutionary change?

-Evolutionary theory explains the existence of homologous structures adapted to different purposes as the result of descent with modification from a common ancestor. -Similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor.

Gene pool

A gene pool consists of all the genes, including all the different alleles for each gene, that are present in a population. Researchers study gene pools by examining the numbers of different alleles they contain.

Molecular clock

A molecular clock uses mutation rates in DNA to estimate the time that two species have been evolving independently.

What are molecular clocks?

A molecular clock uses mutation rates in DNA to estimate the time that two species have been evolving independently.

Temporal isolation

A third isolating mechanism, known as temporal isolation, happens when two or more species reproduce at different times.

What does Darwin's mechanism for evolution suggest about each living and extinct species?

According to the principle of common descent, all species—living and extinct—are descended from ancient common ancestors.

What is a current hypothesis about Galapagos finch speciation?

According to this hypothesis, speciation in Galápagos finches occurred by founding of a new population, geographic isolation, changes in the new population's gene pool, behavioral isolation, and ecological competition.

Allele frequency

Allele frequency is the number of times an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene.

Adaption

Any heritable characteristic that increases an organism's ability to survive and reproduce in its environment is called an adaptation.

How can molecular biology be used to trace the process of evolution?

At the molecular level, the universal genetic code and homologous molecules provide evidence of common descent.

Biogeography

Biogeography is the study of where organisms live now and where they and their ancestors lived in the past

Species

Biologists define a species as a population or group of populations whose members can interbreed and produce fertile offspring.

Analogous structure

Body parts that share common function, but not structure, are called analogous structures.

Sexual selection

But in many species, individuals select mates based on heritable traits, such as size, strength, or coloration, a practice known as sexual selection.

What was Charles Darwin's contribution to science?

Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors.

How is evolution defined in genetic terms?

Evolution, in genetic terms, involves a change in the frequency of alleles in a population over time.

Fitness

Fitness describes how well an organism can survive and reproduce in its environment.

What did Hutton and Lyell Conclude about Earth's History?

Hutton and Lyell concluded that Earth is extremely old and that the processes that changed Earth in the past are the same processes that operate in the present.

How is inherited variation used in artificial selection?

In artificial selection, nature provides the variations, and humans select those they find useful.

Genetic drift

In small populations, individuals that carry a particular allele may leave more descendants than other individuals leave, just by chance. Over time, a series of chance occurrences can cause an allele to become more or less common in a population.

What is genetic drift?

In small populations, individuals that carry a particular allele may leave more descendants than other individuals leave, just by chance. Over time, a series of chance occurrences can cause an allele to become more or less common in a population.

How did Lamarck propose that species evolve?

Lamarck suggested that organisms could change during their lifetimes by selectively using or not using various parts of their bodies. He also suggested that individuals could pass these acquired traits on to their offspring, enabling species to change over time.

What was Malthus's view of population growth?

Malthus reasoned that if the human population grew unchecked, there wouldn't be enough living space and food for everyone.

How do fossils help to document the descent of modern species from ancient ancestors?

Many recently discovered fossils form series that trace the evolution of modern species from extinct ancestors.

Polygenic trait

Many traits are controlled by two or more genes and are called polygenic traits.

Natural selection

Natural selection is the process by which organisms with variations most suited to their local environment survive and leave more off- spring.

Under what conditions does natural selection occur?

Natural selection occurs in any situation in which more individuals are born than can survive (the struggle for existence), there is natural heritable variation (variation and adaptation), and there is variable fitness among individuals (survival of the fittest).

How does natural selection affect single-gene and polygenic traits?

Natural selection on single-gene traits can lead to changes in allele frequencies and, thus, to changes in phenotype frequencies.

Reproductive isolation

Once a population has thus split into two groups, changes in one of those gene pools cannot spread to the other. Because these two populations no longer interbreed, reproductive isolation has occurred

Where do new genes come from?

One way in which new genes evolve is through the duplication, and then modification, of existing genes.

How does the geographic distribution of species today relate to their evolutionary history?

Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors.

Homologous structure

Structures that are shared by related species and that have been inherited from a common ancestor are called homologous structures.

Behavioral isolation

Suppose two populations that are capable of interbreeding develop differences in courtship rituals or other behaviors. Behavioral isolation can occur

What conditions are required to maintain genetic equilibrium?

The Hardy-Weinberg principle predicts that five conditions can disturb genetic equilibrium and cause evolution to occur: (1) nonrandom mating; (2) small population size; and (3) immigration or emigration; (4) mutations; or (5) natural selection.

Bottleneck effect

The bottleneck effect is a change in allele frequency following a dramatic reduction in the size of a population

Speciation

The formation of a new species is called speciation.

What determines the number of phenotypes for a given trait?

The number of phenotypes produced for a trait depends on how many genes control the trait.

Evolution

The process of change over time is called evolution.

Founder effect

This situation, in which allele frequencies change as a result of the migration of a small subgroup of a population, is known as the founder effect.

What are the sources of genetic variation?

Three sources of genetic variation are mutation, genetic recombination during sexual reproduction, and lateral gene transfer.

Vestigial structure

Vestigial structures are inherited from ancestors but have lost much or all of their original function due to different selection pressures acting on the descendant.

Artificial selection

When Humans force evolution to occur, by breeding often to get better animals, plants, etc.

Disruptive selection

When individuals at the outer ends of the curve have higher fitness than individuals near the middle of the curve, disruptive selection occurs.

Directional selection

When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end, directional selection occurs.

Stabilizing selection

When individuals near the center of the curve have higher fitness than individuals at either end, stabilizing selection takes place.

What types of isolation lead to the formation of new species?

When populations become reproductively isolated, they can evolve into two separate species. Reproductive isolation can develop in a variety of ways, including behavioral isolation, geographic isolation, and temporal isolation.

Genetic equilibrium

f a population is not evolving, allele frequencies in its gene pool do not change, which means that the population is in genetic equilibrium.

Single-gene trait

single-gene trait—a trait controlled by only one gene.

Fossils

the remains or impression of a prehistoric plant or animal embedded in rock and preserved in petrified form.