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 allele frequency in a population.

• 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

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 happen

Timing- breeding seasons occur at different times

Reproductive barriers• 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.

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)

Geographic Isolation

Population Evolution

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.

Adaptive radiation

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.

Adaptation Models

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

Complexity of eye

II. Adaptation of Existing Structures to New Functions

A. There are thousands of instances where existing materials or structures evolved into new adaptations

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

C. Sometimes the timing or rate of development plays a role in evolution

Remodeling Process

• Ground and Tree Dwelling

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 fossils

B. Fossils aren’t always bone, they can be footprints, burrows, impressions or even dung

Fossils

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

Geologic Time Scale

Geologic Eras

4.6 bya- Precambrian (cells appear & simple animals)

540 mya- Paloezoic (complex animals & plants)

245 mya- Mesozoic (dinosaurs & mammals)

65 mya- Cenozoic (mammals & humans)

III. Dating Fossils

A. Radiometric dating measures certain radioactive isotopes to determine the ages of rocks and fossils

B. Half-Life is the number of years it takes for 50% of the original sample to decay [y=a(1-r)t ]

C. The half-life is unaffected by temperature, pressure and other environmental conditions

Radioactive Isotopes

• Carbon 14 -> carbon 12 (living -bone, plants)

• Isotope (more neutrons) -> normal• Uranium 238 --> Lead 206

(volcanic rock)• 100% of isotope = present time• Less isotope -> older the material

Radioactive Isotopes and Age

Half-Life

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 life1. 250 million years ago all the plates moved together

forming Pangea2. 180 million years ago Pangea began to break up,

isolating the continents

Continental Drift

V. Mass ExtinctionsA. 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

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

Classification

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 species

Kingdoms

5 Kingdoms

• Monera - bacteria (prokaroyote)• Protista- amoeba (single cell)• Animal- platypus• Plant- fern• Fungi- mushroom• Virus (Non-living?) a kingdom?

III. Classification and Evolution

A. A diagram that reflects evolutionary relationships has a branching pattern called a phylogenetic tree

B. Convergent Evolution is a process in which unrelated species from similar environments have adaptations that seem similar

C. Similar adaptations that result from convergent evolution are called analogous structures

Phylogenic Tree

Classification Groups (Linnanean)

• Kingdom (largest 5 of them) --> Phylum --> Class --> Order --> Family --> Genus --> Species (millions of them)

5 Kingdom / 3 Domain

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

Cladogram

Cladogram

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

Re-examining Classification

Redi’s Experiment