Vocabulary Chapter 15 Artificial selection Natural selection Evolution

Artificial selection The process of directed breeding to produce offspring with desired traits also referred to as selective breeding Example: when humans develop new breeds of dogs or new strains of crop plants

Natural selection There is a competitive struggle for existence in the natural world if some competitors in this struggle are better equipped for survival than others, then those less equipped would die Occurs because there is variation, heritability, overproduction, and reproductive advantages

Evolution Cumulative changes in groups of organisms (species) through time Natural selection is a mechanism of how this change occurs

Vocabulary Chapter 15 Derived trait Ancestral trait Homologous structure Vestigial structure Analogous structure

Derived Traits Newly evolved traits, that may not appear in the fossils of common ancestors When studying transitional fossils traits may be classified in two major categories either derived traits or ancestral traits Example: With Archaeopteryx fossils (possible ancestor to modern birds with distinct dinosaur features) the derived traits like feathers do not appear in the fossils of common ancestors

Ancestral Traits More primitive traits, that do appear in the fossils of common ancestors Example: In Archaeopteryx fossils the ancestral traits may be the teeth and tails that do appear in ancestral forms

Homologous Structures Anatomically similar structures inherited from a common ancestor May have different function Examples: The forelimbs of vertebrates show homologous structures. The limbs are adapted for different uses, but they all have similar bones.

Vestigial structures Structures that may no longer have a function for that species and are reduced in form May resemble functional structures in other organisms Examples: Snake pelvis and human appendix

Analogous Structures Structures that can be used for the same purpose and can be superficially similar in construction but are not inherited from a common ancestor Example: Wings of an eagle and the wings of a beetle have the same function (flight) but the wings are constructed in different ways and from different material

Vocabulary Chapter 15 Embryo Biogeography Fitness Camouflage Mimicry

Embryo An early, pre-birth stage of an organisms development Comparative embryology – vertebrate embryos exhibit homologous structures during certain phases of development but become totally different structures in the adult forms Example: Vertebrate embryos have a tail and pharyngeal pouches (in fish develop into gills, in reptiles, birds, and mammals become part of the ears, jaws and throats

Biogeography Study of the distribution of plants and animals around the world

Fitness A measure of the relative contribution that an individual trait makes to the next generation Reproductive success Measured as the number of reproductively viable offspring that an organism produces in the next generation

Camouflage Morphological adaptation that allows individuals of a species to blend in with their environment Allows organisms to become almost invisible to predators or prey, as a result more of the camouflaged individuals survive and reproduce

Mimicry Morphological adaptation where one species evolves to resemble another species Example: Mimicry can occur in a harmless species that has evolved to resemble a harmful species, such as the California kingsnake color patterns mimicking those of the poisonous western coral snake

Vocabulary Chapter 15 Genetic drift Founder effect Bottleneck

Genetic Drift Change in allelic frequencies in a population that results from chance A random circumstance causes a certain genetic trait to become more common or rarer over time Example: A man steps on a group of beetles, randomly killing most of the green ones but leaving most of the brown ones alive, resulting in fewer green beetles being produced in the population

Founder Effect Occurs when a small sample of a population settles in a location separated from the rest of the population Alleles that were uncommon in the original population might be common in the new population and the offspring in the new population will carry those alleles Example: Amish seldom marry outside of their immediate community, in the Old Order Amish community there is a high frequency of six-finger dwarfism, affected individuals can trace their ancestry back to one of the founders of the Order

Bottleneck Occurs when a population declines to a very low number and then rebounds Results in decreased genetic variation Example: Northern elephant seals where hunted by humans almost to extinction leaving only 20 individuals left in the late 1890’s, since there population has rebounded to over 30,000 but the reduced genetic variation in the population is apparent