Download Concept 15.2: Evolution is usually a remodeling process

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Concept 15.1: The diversity of life is based on the origin of new species
I. What is a Species?
A. Biologist define a species as a population whose members have the ability to breed with one another in
nature and produce fertile offspring.
B. This is referred to as the Biological Species Concept
II. From Microevolution to Macroevolution
A. Earlier we saw microevolution refers to a change in the
B. Macroevolution is a dramatic change
 New species evolving (speciation)
 Extinction of species
 New features of living things
C. Speciation leads to an increase in biologic diversity
allele frequency in a population.
III. Reproductive barriers between species
A. Reproductive isolation is a condition that keeps two species from interbreeding. Reproductive
isolation usually involves two or more of the following, but just one is sufficient for isolation to
 Timing- breeding seasons occur at different times
 Behavior- different mating behaviors prevent successful mating
 Habitat- species are adapted to specific habitats in the same area and don’t interact
 Structure- reproductive structures are incompatible
 Sterility- mating may occur but offspring are sterile due genetic differences
IV. Geographic isolation and Speciation
A. When one species becomes physically separated into two populations, the separation may lead to
two distinct species through microevolution. This is called Geographic isolation.
B. Species can become geographically isolated from each other in two ways
1. Geography of the Earth may change and separate a species
2. The species may be dispersed or moved to different point on the globe by other methods
(stowaways on ships or planes)
V. Adaptive Radiation
A. When multiple species arise from one common ancestor and spread-out to and adapt to different
habitats this is known as Adaptive Radiation.
B. The numerous types of finches in the Galapagos Islands are an example of adaptive radiation.
VI. Tempo or Speed of Speciation
When species diverge in spurts of relatively rapid change, then these new species may remain
unchanged for an extremely long period in the fossil record this is known as Punctuated Equilibrium.
Concept 15.2: Evolution is usually a remodeling process
I. Refinement of Existing Adaptations
A. Complex structures may have evolved from a similar structure having the same basic function
B. An example of this would be the eye which has many interacting parts
II. Adaptation of Existing Structures to New Functions
A. There are thousands of instances where existing materials or structures evolved into new
B. Chitin originated to help marine animals from predators, now it is found in land animals and it is
used to fight dehydration
C. The flippers of penguins are another example of using old structures for new functions
III. Evolution and Development
A. Embryology is the study of the processes of multicellular organisms as they develop from
fertilized eggs to fully formed organisms
B. Genes that control the development of an organism are of particular importance
Sometimes the timing or rate of development plays a role in evolution
Concept 15.3 The fossil record provides evidence of life’s history
I. How Fossils Form
A. Soft body parts usually decay quickly, and hard parts like bone, teeth and shells may become
B. Fossils aren’t always bone, they can be footprints, burrows, impressions or even dung
II. The Fossil Record and Geologic Time Scale
A. The Geologic Time Scale organizes Earth’s History into four distinct ages known as the
Precambrian, Paleozoic, Mesozoic and Cenozoic Eras
B. Eras are divided into periods and the periods are divided into epochs
C. New eras are recognized by a major change in the life forms of that time
III. Dating Fossils
A. Radiometeric dating measures certain radioactive isotopes to determine the ages of rocks and
Half-Life is the number of years it takes for 50% of the original sample to decay
The half-life is unaffected by temperature, pressure and other environmental conditions
IV. Continental Drift and Macroevolution
A. Landmasses on different plates change position relative to one another known as continental drift
B. There are two major events of continental drift that had a major impact on the history of life
1. 250 million years ago all the plates moved together forming Pangea
180 million years ago Pangea began to break up, isolating the continents
V. Mass Extinctions
A. Earth had relatively long periods of stability broken by brief episodes of great species loss known
as mass extinctions
B. Extinctions occur all the time but there have been five or six distinct periods of mass extinction
over the last 600 million years
C. After every extinction the surviving organisms have a new opportunity to change
Concept 15.4 Modern taxonomy reflects evolutionary history
I. What is Taxonomy?
A. Taxonomy involves the naming and classification of organisms
B. The goal is to reduce confusion and organize life into larger groups or related species
II. The Linnaean System of Classification
A. Carolus Linnaeus developed a system that uses a two part Latin name for each species and a
hierarchy of species into broader groups
B. The two part name is binomial which means the first name is the genus and the second name is the
III. Classification and Evolution
A. A diagram that reflects evolutionary relationships has a branching pattern called a phylogenetic
Convergent Evolution is a process in which unrelated species from similar environments have
adaptations that seem similar
Similar adaptations that result from convergent evolution are called analogous structures
IV. Molecular Data as a Taxonomic Tool
A. The relatedness of species can be measured by comparing genes and gene products
B. This evidence is independent of structural data
V. Cladistics
A. Cladistics is the scientific search for ancestral relationships among species
B. Each branch on a cladogram is called a clade; every clade consists of an ancestral species and all of
its descendants
C. Derived characters are homologous characteristics that unite the organisms as a group
VI. Comparing Classification Schemes
A. The Kingdom is the broadest taxonomic category
B. Biologists have gone from a two-kingdom system, three-kingdom system, five-kingdom system
and now to a three domain system