Topic 11 Speciation and Origin of life 35-66

punctuated equilibrium

Pattern of evolution in which long stable periods are interrupted by brief periods of more rapid change

gradualism

A way of describing the tempo of evolution as the sum of many small changes

heterochrony

A change that causes variation in the timing of growth of different body parts and can lead to phenotypic differences

allometric growth

A change that causes different part of the body to grow at different rates

paedomorphosis

The retention in an adult organism of the juvenile features of its evolutionary ancestors

homeotic genes

Master regulatory genes that determine the placement and spatial organization of body parts

phylogeny

The study of evolutionary relationships among groups of organisms

systematics

A branch of biological classification that seeks to classify organisms using a combination of phylogenetic relationship and degree of evolutionary changes

morphology

A branch of biology dealing with the study of the form and structure of organisms and their specific structural features

analogies

Features from different organisms that have separate evolutionary origins, but are superficially similar due to convergent evolution

cladistics

Biological classification in which organisms are grouped together based on whether they have one or more shared unique characters

cladograms

Diagrams used in cladistics which shows relations among organism

monophyletic

A grouping of organisms that consists of an ancestral species and all its descendants

paraphyletic

A grouping of organisms that consist of an ancestral species and some but not all of its descendants

polyphyletic

A grouping of organisms that includes organisms but not all of their common ancestors

homologous structures

Similar anatomical structures of different species that have a shared ancestry

outgroup

Group of organisms that serve as a reference group for determining the evolutionary relationship among groups of organisms

shared primitive character

Characteristics shared by all members of the group being compared

shared derived character

Characteristics shared by only some members of the group

principle of maximum parsimony

A theory stating that the preferred phylogenetic tree is the tree that supposes the fewest evolutionary change events

principle of maximum likelihood

A method in which phylogenetic trees are scored based on a character dataset, and the tree with the best score is selected

gene duplications

Any repetition of a region of DNA that contains a gene

gene family

A set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions

orthologous genes

Genes found in different species that are may have changed only after speciation

paralogous genes

Copies of genes that have diverged from one another within a species

molecular clocks

A way to measure the absolute time of evolutionary changes based on the observation that some genes and other regions of genomes appear to evolve at constant rates

panspermia

The hypothesis that life exists throughout the Universe, distributed by meteoroids, asteroids, comets and planetoids

protobionts

The combination of abiotically produced organic molecules surrounded by a membrane-like structure that are considered to have possibly been the precursors to first cells

RNA World

A hypothesis that proposes that self-replicating RNA molecules were precursors to current life

radiometric dating

A technique used to date materials based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products

mass extinction

An event in which large numbers of species become extinct throughout earth

endosymbiotic theory

A theory that states several key organelles of eukaryotes (such as mitochondria and plastids), originated as symbioses between separate single-celled organisms