Unit 7: Natural Selection

Gene flow

________ can occur between different populations of the same species if individuals migrate.

Stanley Miller

________ and Harold Urey simulated the conditions of primitive Earth in a laboratory.

Charts

________ called phylogenetic trees, or cladograms, are used to study relationships between organisms.

extreme traits

Stabilizing selection means that organisms in a population with ________ are eliminated.

Evolution

________ is a change in a population over time.

Natural selection

________ is defined in terms of populations but occurs in terms of individuals.

Fitness varies

________ based on biotic and abiotic factors; different genetic variations can be selected for in different generations.

Evolutionary fitness

________ is measured by reproductive success.

Convergent evolution

________ is the process by which two unrelated and dissimilar species come to have similar traits, often because they have been exposed to similar selective pressures.

Cladograms

________ are often drawn with even spacing between species, but phylogenetic trees are often drawn with different distances between species and as a result they look more like a tree with uneven branches.

Biotic

________ and abiotic factors can affect the direction of evolution.

Morphological homologies

________, or the study of the anatomy of various animals: scientists discovered that some animals have similar structures that serve different functions.

Divergent evolution

________ that occurs quickly after a period of stasis is called punctuated equilibrium.

fittest offspring

The ________, or those with the most favorable traits, are the most likely to survive and therefore produce a second generation.

next generation

As long as a mutation does not kill an organism before it reproduces it may be passed on to the ________.

Hardy Weinberg law

The ________ states that even with all the shuffling of genes that goes on, the relative frequencies of genotypes in a population are constant over time.

environmental impact

If the population is small, the population will be more susceptible to random ________ than if the population is large.

post zygotic barrier

A(n) ________ is related to the inability of a hybrid organism to produce offspring.

genetic equilibrium

If mutations are present in a population, new alleles will be introduced into the population and hence ________ will be disturbed.

Survival

________ of the fittest is the name of the game, and any trait that causes an individual to reproduce better gives that individual evolutionary fitness.

Allopatric speciation

________ simply means that a population becomes separated from the rest of the species by a geographic barrier so the two populations cant interbreed.

original life form

Some ________ is the common ancestor to all life.

Genetic drift

________ is something that causes a change in the genetics of a population, but it is not natural selection.

Molecular Biology

________: The most compelling proof of all is the similarity at the molecular level.

Genetic variation

________ is the very foundation of evolution.

Phylogenetic trees

________ are built using data from the fossil record or molecular record.

Natural selection

________ requires genetic variation and an environmental pressure.

Natural selection

________ occurs only if some individuals have more evolutionary fitness and can be selected.

natural selection

If there is ________, organisms better adapted to their environment will be more likely to survive and reproduce, and thus their alleles will be preferentially propagated to the next generation.

Paleontology

paleontology revealed the various organisms and the major lines of evolution

Biogeography, or the study of the distribution of flora (plants) and fauna (animals) in the environment

scientists found related species in widely separated regions of the world

Embryology, or the study of development of an organism

All the vertebrates-including fish, amphibians, reptiles, birds, and even mammals such as humans-show fishlike features called gill slits

Morphological homologies, or the study of the anatomy of various animals

scientists discovered that some animals have similar structures that serve different functions

Molecular Biology

The most compelling proof of all is the similarity at the molecular level

Continuing Evolution

Evolution is constantly occurring