Bio The Origin & Evolution of life

Natural selection, also known as “survival of the fittest,”

the more prolific
reproduction of individuals with favorable traits that survive environmental
change because of those traits; this leads to evolutionary change.
• First, most characteristics of organisms are inherited, or passed from
parent to offspring.
• Second, more offspring are produced than are able to survive, so
resources for survival and reproduction are limited.
• Third, offspring vary among each other in regard to their characteristics
and those variations are inherited

PROCESSES AND PATTERNS OF EVOLUTION

Natural selection can only take place if there is variation, or differences,
among individuals in a population.
• Genetic diversity in a population comes from two main mechanisms:
mutation and sexual reproduction.
• Mutation, a change in DNA, is the ultimate source of new alleles, or
new genetic variation in any population.
• Sexual reproduction also leads to genetic diversity: when two parents
reproduce, unique combinations of alleles assemble to produce the
unique genotypes and thus phenotypes in each of the offspring.

adaptation

A heritable trait that helps the survival and reproduction of an organism in
its present environment is called

divergent evolution

When two species evolve in diverse directions from a common point, it is
called

Convergent evolution

similar traits evolve independently in species that
do not share a recent common ancestry

Fossils

provide solid evidence that organisms from the past are not the same
as those found today, and fossils show a progression of evolution.

homologous structures

The similar construction of these appendages indicates that these organisms share a
common ancestor.
Scientists call these synonymous parts

Phylogeny

describes the relationships of an organism, such as from which organisms it is thought
to have evolved, to which species it is most closely related, and so forth.

phylogenetic tree

is a diagram used to reflect evolutionary
relationships among organisms or groups of organisms.

Both of these phylogenetic trees shows the relationship of the three domains of life—
Bacteria, Archaea, and Eukarya

rooted tree

attempts to identify when
various species diverged from a common ancestor while the

root

of a phylogenetic tree indicates that an ancestral lineage gave rise to all organisms
on the tree

branch point

indicates where two lineages diverged

basal taxon

A lineage that evolved
early and remains unbranched is a

sister taxa

When two lineages stem from the same
branch point, they are

polytomy

A branch with more than two lineages is

systematics

Information is used to organize and classify organisms based on evolutionary
relationships in a scientific field called

Taxonomy

which literally means “arrangement law”) is the science of
classifying organisms to construct internationally shared classification systems
with each organism placed into more and more inclusive groupings. Each level is
a taxon

domain

is a second category called a kingdom

kingdoms

the subsequent categories of increasing specificity are: phylum, class, order,
family, genus, and species

binomial nomenclature

Scientists generally refer to an organism only by
its genus and species, which is its two-word
scientific name (italicized), in what is

taxonomic classification system

uses a hierarchical model to organize living
organisms into increasingly specific categories. The common dog, Canis lupus
familiaris, is a subspecies of Canis lupus, which also includes the wolf and dingo

Dalbergia sissoo (D. sissoo) is in the
Fabaceae, or legume family

Scientists found that D. sissoo shares a DNA
marker with species within the Fabaceae
family that have antifungal properties.
Subsequently, D. sissoo was shown to
have fungicidal activity, supporting the
idea that DNA markers can be used to
screen for plants with potential medicinal
properties.

homologous structures

Bat and bird wings are… indicating that bats and birds share a
common evolutionary past

analogy or homoplasy

When similar characteristics occur because of environmental constraints and not
due to a close evolutionary relationship, it is called an

cladistics

After the homologous and analogous traits are sorted, scientists often organize the
homologous traits using a system called…
This system sorts organisms into clades: groups of organisms that descended from a single ancestor

Gene fusion

between different species of prokaryotes when two symbiotic
organisms become endosymbiotic: This occurs when one species is taken
inside the cytoplasm of another species, which ultimately results in a
genome consisting of genes from both the endosymbiont and the host. Three alternate hypotheses of eukaryotic and prokaryotic evolution are (a) the nucleus
first hypothesis, (b) the mitochondrion-first hypothesis, and (c) the eukaryote-first
hypothesis

Ficus

In W. Ford Doolittle's (a) phylogenetic model, the “tree of life” arose from a community
of ancestral cells, has multiple trunks, and has connections between branches where
horizontal gene transfer has occurred. Visually, this concept is better represented by (b)
the multi-trunked. than by an oak's single trunk similar to Darwin's tree

“ring of life” phylogenetic model

the three domains of life evolved from a pool of primitive prokaryotes