Biology Chapter: Natural Selection and Variation

The study of similarities and differences in the anatomy of organisms to understand evolutionary relationships.

A structure in an organism that is no longer functional but was present and functional in its ancestors. An example is the appendix in humans.

The study of similarities and differences in the development of embryos of different organisms to understand evolutionary relationships.

The branch of biology that studies the similarities and differences in the DNA and RNA of organisms to understand evolutionary relationships.

All living organisms share DNA as their genetic material.

Structures that are similar in form and function in different species, but have different evolutionary origins. This suggests that these structures arose independently in different lineages.

Structures that are similar in form and function in different species, and share a common evolutionary origin. This suggests that these structures are inherited from a common ancestor.

A structure that is similar in form but has a different function in different species. This suggests that these structures have been modified from a common ancestor over time to serve different purposes.

A technique for estimating when organisms diverged from a common ancestor by comparing the number of genetic differences in their DNA sequences.

The study of fossils, the remains or traces of ancient organisms, provides evidence for the evolution of life on Earth.

The discovery of fossils that show transitional forms between different groups of organisms strengthens the evidence for evolution.

The study of evolution relies on multiple lines of evidence. Fossil records, comparative anatomy, comparative embryology, and molecular genetics all contribute to our understanding of how life has changed over time.

The concept that individuals within a population show differences in their traits due to underlying genetic variations.

Natural selection is the process where organisms with traits better suited to their environment are more likely to survive and reproduce, passing on those traits to their offspring.

Anything that restricts population growth, such as limited resources, predation, or disease.

The process by which the frequency of genes within a population changes over multiple generations, leading to evolution and potentially speciation.

The process of creating new species through the accumulation of genetic changes over generations.

A type of natural selection where individuals at both extreme ends of a trait distribution are favored, leading to the development of two distinct populations.

An organism's ability to survive and reproduce in a particular environment.

The phenotypic variations that make some individuals more likely to survive and reproduce due to limiting factors in the environment.

The process by which populations evolve over generations due to the unequal survival and reproduction of individuals with different traits.

The proportion of a particular gene variant (allele) in a population.

Variations within a population arise from pre-existing genetic differences.

Competition for resources, predation, and disease are examples of limiting factors that influence survival rates.

The passing of alleles from generation to generation due to reproductive success.

A change in the frequency of alleles in a population over generations.

The formation of new and distinct species in the course of evolution.

Differential survival and reproduction leads to a shift in the frequency of traits within a population.

The theory that all species descended from common ancestors over time.

A type of natural selection where extreme phenotypes are eliminated, favoring average traits. This prevents divergence from the original form and function and is the most common type.

A type of natural selection where one extreme phenotype is favored, causing a shift in allele frequency in one direction. This can occur due to environmental changes or migration to new areas with different pressures.

A type of natural selection where two extreme phenotypes are favored, while average traits are selected against. This can lead to the development of distinct sub-populations.