Biology Exam 1

What is genetic variation?

Differences in DNA sequences among individuals in a population.

How can patterns of genetic variation be described?

By allele frequencies.

What is evolution in biological terms?

A change in the frequency of alleles or genotypes in a population over time.

What leads to adaptations in organisms?

Natural selection enhances the fit between an organism and its environment.

What are nonadaptive mechanisms of evolution?

Migration, mutation, genetic drift, and non-random mating.

What is molecular evolution?

A change in DNA or amino acid sequences over time.

What is a gene pool?

All the alleles present in all individuals of a species.

Define a population in biological terms.

An interbreeding group of organisms of the same species living in the same geographic area.

What does 'variable' mean in the context of genetic variation?

Differences around the mean value of a measured trait.

What is a phenotype?

The physical appearance or observable traits of an organism, coded for by its genotype.

What is the difference between homozygous and heterozygous genotypes?

Homozygous means having identical alleles, while heterozygous means having different alleles.

How is allele frequency calculated?

By dividing the number of a particular allele by the total number of allele placements in the population.

What is the Hardy-Weinberg Equilibrium Model?

A model that describes a population that is not evolving, based on specific assumptions.

List one assumption of the Hardy-Weinberg Equilibrium.

There are no differences in survival and reproductive success of individuals in the population.

What is the significance of measuring observable physical traits in evolution?

They provide a way to assess changes in allele or genotype frequencies over time.

What is gel electrophoresis used for in evolutionary biology?

To compare the relative size of genes and assess genetic variation.

What is DNA sequencing used for?

To determine the specific genetic code and assess genetic variation.

What does 'pheno' mean in the context of genetics?

'Pheno' refers to showing, seeming, or appearing, as in phenotype.

What does 'geno' refer to in genetics?

'Geno' refers to offspring or genes.

What is the role of mutations in evolution?

Mutations introduce new genetic variations that can affect allele frequencies.

What is genetic drift?

A mechanism of evolution that involves random changes in allele frequencies in a population.

What role does natural selection play in evolution?

It leads to adaptations that enhance the fit between an organism and its environment.

What are the assumptions of the Hardy-Weinberg Equilibrium model?

No differential survival or reproductive success, no migration, no mutation, large population size, and no mate choice.

What is gene flow?

Migration, which is considered the great equalizer in populations.

What is the heterozygote advantage?

The phenomenon where heterozygous individuals have a higher fitness than homozygous individuals.

What is inbreeding depression?

A severe form of non-random mating that can lead to reduced biological fitness.

What is the significance of natural selection in evolutionary theory?

It is a cornerstone that explains how certain traits become more common over time.

What is disruptive selection?

A type of natural selection that favors extreme traits over intermediate traits.

What is stabilizing selection?

A type of natural selection that favors average traits and reduces variation.

What is directional selection?

A type of natural selection that favors one extreme phenotype over others.

What is the relationship between natural selection and reproductive success?

Individuals with certain heritable traits are more likely to survive and reproduce.

What is a genotype?

The genetic constitution of an individual, specifically regarding a particular trait.

How does natural selection affect allele frequencies?

It causes changes in allele frequencies over long periods as advantageous traits become more common.

What are the core concepts of evolutionary biology?

Genetic variation, allele frequencies, evolution, natural selection, nonadaptive mechanisms, and molecular evolution.

What is the fundamental job of biology?

To understand speciation, the process that produces new and distinct forms of life.

What would happen in a world without speciation?

There would be a single kind of generally adapted organism, resulting in a lack of biological diversity.

What is the estimated number of species on Earth?

Between 10 and 100 million species.

What is the key to the biological species concept?

Reproductive isolation.

What causes reproductive isolation?

Barriers to reproduction before or after egg fertilization.

Who first established the definition of 'species'?

Alfred Russell Wallace.

How did Ernst Mayr define species?

As groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups.

What is the morphospecies concept?

A rule of thumb that most individuals of the same species look alike, used to identify species.

What is hybridization?

When closely related species can reproduce.

What is the Wallace Effect?

There should be selection against hybridization.

What are the two categories of reproductive isolation?

Pre-zygotic (before fertilization) and post-zygotic (after fertilization).

What are examples of pre-zygotic barriers?

Behavioral, physical, temporal, and ecological barriers.

What is allopatric speciation?

Speciation that occurs when populations become geographically isolated.

What is peripatric speciation?

A special case of allopatric speciation where a small population is isolated at the edge of a species' range.

What is adaptive radiation?

Rapid speciation that occurs when organisms adapt to a variety of ecological niches.

What is co-speciation?

When two organisms speciate in response to each other.

What is sympatric speciation?

Speciation that occurs in the same geographic area, often due to disruptive selection.

What is instantaneous speciation?

A type of speciation that occurs rapidly, often through mechanisms like polyploidy.

What is polyploidy?

A condition in which an organism has more than two complete sets of chromosomes, leading to speciation.

How can speciation occur in the absence of natural selection?

Through genetic drift in allopatric populations.

What role does natural selection play in speciation?

It can facilitate speciation, especially in allopatric populations through adaptive radiation.

What is reinforcement of reproductive isolation?

Natural selection favors pre-zygotic isolation mechanisms to prevent hybridization.

What are the limitations of the biological species concept?

It cannot be applied to asexual or extinct organisms and does not account for genetic exchange in ring species.

What is the significance of speciation?

It underlies the diversity of life on Earth.

What is a phylogenetic tree?

A reasoned hypothesis of the evolutionary relationships among organisms.

What basis is used to construct a phylogenetic tree?

Shared derived characters.

What does the fossil record provide evidence for?

Direct evidence of evolutionary history.

How do phylogeny and fossils support the theory of evolution?

They provide independent and corroborating evidence of evolution.

What is a polytomy in phylogenetics?

A node with more than two immediate descending branches, indicating uncertainty in relationships.

What are sister groups in a phylogenetic tree?

Taxa that share a most recent common ancestor that is not shared with any other taxon.

What are monophyletic groups?

Groups that include all descendants of a common ancestor and only those descendants.

What is binomial nomenclature?

A system for naming species using a genus and a specific epithet, both italicized.

How is the genus name abbreviated in binomial nomenclature?

By shortening it to the single capitalized first letter followed by the specific epithet.

What is a synapomorphy?

A shared derived character used to define a group in phylogenetics.

What distinguishes homologous characters from analogous characters?

Homologous characters are derived from a common ancestor, while analogous characters arise due to similar selective environments.

What is the significance of branch lengths in a phylogenetic tree?

They can represent time or the degree of divergence between species.

What is the role of mass extinctions in evolution?

They alter the course of evolution by eliminating important groups of species and opening new possibilities.

What is the geologic timescale used for?

To represent the timing of evolutionary events and the appearance of new groups.

What does the term 'extant sister group' refer to?

The closest living relative of a group of organisms.

What is the importance of Tiktaalik in evolutionary biology?

It represents a transitional form between fish and tetrapods, showcasing mixed traits.

What is the difference between paraphyletic and polyphyletic groups?

Paraphyletic groups include a common ancestor and some descendants, while polyphyletic groups do not include the common ancestor.

What is the significance of molecular sequences in phylogenetics?

They help reveal evolutionary relationships and the classification of organisms into domains.

What are the three domains of life revealed by molecular sequences?

Bacteria, Archaea, and Eukarya.

What is a trace fossil?

Fossils that provide evidence of the activity of organisms, such as footprints or burrows.

What is the role of isotopes in radiometric dating?

Isotopes like Carbon-14 are used to determine the age of fossils based on their decay rates.

What does the term 'amniotic egg' refer to?

An egg that contains a protective amniotic membrane, characteristic of sauropsids and mammals.

What is the significance of shared ancestral characteristics in phylogenetics?

They help define relationships among taxa but are not modified in all taxa.

What is the importance of the fossil Eusthenopteron?

It is a key transitional fossil that provides insight into the evolution of tetrapods from fish.

What is the main goal of constructing a phylogenetic tree?

To break down evolutionary relationships into dichotomous, monophyletic sister groups.

What does 'species' refer to in biological classification?

An invariable word that has no form specific to singular or plural.

What is the correct format for writing a species name?

Italicized, with the genus capitalized and the specific epithet in lowercase.

What evidence shows that the human lineage branches off the tree of great apes?

Anatomical, molecular, and fossil evidence.

Where did our species arise according to phylogenetic analysis?

In Africa.

How long ago did the human lineage acquire distinctive features since the common ancestor with chimpanzees?

5-7 million years.

What has had an important impact on patterns of genetic variation in humans?

Human history.

What remarkable developments are seen in humans?

Culture, language, and consciousness.

What is the earliest known member of the hominin lineage?

Sahelanthropus tchadensis.

How old is the Sahelanthropus tchadensis specimen?

About 7 million years old.

What features does Sahelanthropus tchadensis combine?

Modern human and ancestral features.

Did modern humans evolve from chimpanzees?

No, they share a common ancestor.

How long have hominins been walking upright?

At least 3.2 million years.

What was Ardipithecus ramidus (Ardi) known for?

Being bipedal on land but quadrupedal in trees.

What significant change occurred in hominins between Ardi and Lucy?

Hominins became fully bipedal.

What does the genus Homo include?

Many different species of hominins.

What does the increase in brain size in hominins correlate with?

Increases in body size.

What are the two hypotheses regarding modern human evolution?

The Multiregional Hypothesis and the Out-of-Africa Hypothesis.