Unit 7 Natural Selection Flashcards

Review flashcards for Unit 7 Natural Selection, covering Hardy-Weinberg equilibrium, RNA World Hypothesis, comparative morphology, molecular homology, and various evolutionary concepts.

Hardy-Weinberg equilibrium

Model that determines genetic makeup of a population that is not evolving so that it can be compared to the genetic makeup of a population.

RNA World Hypothesis

Suggests that RNA (not DNA or proteins) is what stores genetic information.

Comparative morphology

Analysis of the structures of living and extinct organisms.

Molecular homology

Many species share similar DNA and amino acid sequences.

Homology

Characteristics in related species that have similarities even if the functions differ.

Analogous structures

Structures that are similar but have separate evolutionary origins.

Homologous structures

Characteristics that are similar in two species because they share a common ancestor.

Vestigial structures

Structures that are conserved even though they no longer have a use.

Convergent evolution

Similar adaptations that have evolved in distantly related organisms due to similar environments.

Node

A hypothetical last common ancestor on phylogenetic trees.

Cladogram

Hypothetical relationships between species in terms of morphology.

Monophyletic group

Section of a phylogenetic tree that shows a common ancestor and its descendants.

Synapomorphy

Characteristic derived from a common ancestor that two or more species share.

Outgroup

The most distantly related organism in a cladogram.

Basal taxon

Species on a phylogenetic tree that branches off early.

Derived characteristic

Characteristic that appears over generations and wasn’t present in an ancestor.

Paraphyletic group

Section of a phylogenetic tree that shows organisms where some share a common ancestor but not all.

Phylogenetic tree

A family tree that follows relationships of different species and common ancestors

Sister taxa

Organisms that are each other’s closest relative on a phylogenetic tree, sharing a node.

Ancestral characteristic

Characteristics that are present in descendants because they were in ancestors

Polyphyletic group

Section of a phylogenetic tree that shows organisms that don’t share a common ancestor

Species

A group able to interbreed and produce viable, fertile offspring

Speciation

formation of new species (impacted by geography)

Temporal isolation

species breed at different times of the day, year, or season

Sympatric speciation

a new species evolves in the same geographic area as the ancestral species

Reduced hybrid viability

The genes of different parent species may interact in ways that impair the hybrid’s development or survival

Macroevolution

large evolutionary patterns (ex. adaptive radiation, mass extinction)

Divergent evolution

groups with the same common ancestor evolve and accumulate differences resulting in the formation of a new species

Gametic isolation

proteins on the surface of gametes do not allow for the egg and sperm to fuse

Habitat isolation

Species live in different areas or they occupy different habitats within the same area

Prezygotic barrier

Things that stop fertilization from happening

Behavioral isolation

unique behavioral patterns and rituals separate species

Reduced hybrid fertility

a hybrid can develop into a healthy adult, but it is sterile

Hybrid breakdown

the hybrid of the first generation may be fertile, but when they mate with a parent species or one another, their offspring will be sterile

Microevolution

change in allele frequencies within a single species or population (natural and sexual selection, genetic drift, gene flow)

Postzygotic barrier

Things that prevent speciation (breeding between species) after reproduction

Mechanical isolation

the reproductive anatomy of one species does not fit with the anatomy of another species

Punctuated equilibrium

when evolution occurs rapidly after a long period of no change

Gradualism

when evolution occurs slowly over hundreds, thousands, or millions of years

Allopatric speciation

a physical barrier separates species, geographically isolated

Adaptive radiation

if a new habitat or niche becomes available, species can diversify rapidly

Natural selection

A trait gives an organism an advantages over others so that it allows the organism to survive enough to reproduce

Fitness

How fit an organism is to reproduce

Differential survival / reproduction

Some traits will allow organisms to outcompete others for resources and more likely to survive and reproduce

Evolution

Change in frequency of inherited genes in a population over multiple generations

Biotic factors

Living factors of an ecosystem (ex. plants, animals)

Abiotic factors

Nonliving factors of an ecosystem (ex. sunlight, water)

Variation

Different versions of the same trait. More variation is better for a population’s longevity.

Selective pressure

A factor that increases or decreases the reproductive success of a population. Positive pressure increases that trait’s percentage, negative decreases

Adaptation

Frequency of the advantageous traits will increase in a population over generations

Gene flow

The transfer of alleles into or out of a population due to fertile individuals or gametes

Mutation

change in the DNA sequence of an organism

Genetic drift

chance events that cause a change in allele frequency from one generation to the next, leads to loss of variation, can cause harmful alleles to be fixed

Bottleneck effect

When a large population is reduced by a non-selective disaster

Founder effect

When individuals become isolated from a large population and establish a new small population in the gene that differs from the large population, loses genetic diversity

Nonrandom mating

When organisms are more or less likely to mate with each other

Artificial selection

humans purposefully breeding animals to select for desirable traits

Population

a group of individuals of the same species that live in the same area and interbreed to produce fertile offspring, consists of all types of alleles

Gene pool

a population’s genetic makeup

Allele frequency

How common an allele is in a population

Directional selection

Gene flow, certain members of a population have certain phenotypes that eventually move toward one direction (ex. People getting taller overall) can lead to new species

Disruptive selection

Selective pressures cause a certain trait to be less expressed in a population (ex. People becoming either taller or shorter but not medium height) can lead to new species

Stabilizing selection

Maintaining of certain traits over time, cannot create new species

Sexual selection

a type of natural selection that explains why many species have unique/showy traits

Fixed / fixed allele

When there’s only one allele type present in a gene pool

Biological species concept

Species that interbreeds and produces viable, fertile offspring

Reproductive barrier

Factors that prevent speciation between two different species

Reproductive isolation

organisms from the two populations cannot pass on their genetic code through reproduction for several generations.