Chapter 15

Origins of Biological Diversity

15.1 Diversity of Life

• biological species concept: defines a species as a population or group of populations whose members have the ability to breed with one another in nature and produce fertile offspring.– asexual reproducers not

included– fossils also not included

Macroevolution

• macroevolution: dramatic biological changes

• origin of different species

• extinction of species• evolution of major

features

• speciation: origin of a new species

• Biological diversity

Reproductive Barriers

• Timing– different breeding seasons

• Behavior– different courtship or mating

behaviors

• Habitat– adapted to different habitats in

the same area

• Others– reproductive structures

incompatible– zygote fails to develop– hybrid cannot reproduce (ex.

mules, wolf hybrids)

reproductive isolation: reproductive barrier keeps two species from breeding

Geographic Isolation• geographic

isolation: separation of populations as a result of geographic change or dispersal to geographically isolated places– separation of

“splinter” populations is crucial to evolution; genetic drift

Adaptive Radiation

• adaptive radiation: evolution from a common ancestor that results in diverse species adapted to different environments– Hawaiian islands; different species on each island

Punctuated Equilibrium

• punctuated equilibrium: species often diverge in spurts of relatively rapid change– Long periods of little

change in a species are broken by shorter times of speciation

– Successful species last 1-5 million years; unique changes in first 50,000 years

15.2 Remodeling Process

• Refinement of Existing Adaptations– Complex structure may have evolved from a simpler

structure having the same basic function– Example: eye refinement – light-sensitive cells

Adaptation of Existing Structures to New Functions

• chitin – forms the exoskeleton of arthropods; protection in ocean– land-dwelling – resists water loss

• Penguins have modified wings for swimming

Evolution and Development

• embryology: study of the processes of multicellular organisms as they develop from fertilized eggs to fully formed organisms– mutation in master control gene has bizarre

effects; cow with head-leg– less dramatic; subtle changes in development– feet of salamanders slightly different based on

habitat; trees vs. land

15.3 Fossil Record

• geologic time scale: organizes Earth's history into four distinct ages known as the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras– Era Period

Epoch

Dating Fossils

• relative age: reflect the order in which groups of species existed compared to one another

• absolute age: actual age in years

• radiometric dating: based on the measurement of certain radioactive isotopes in objects– isotopes have fixed rate

of decay

• half-life: the number of years it takes for 50 percent of the original sample to decay– Uranium-238 : half-life of 4.5

billion years, has been used to date rocks of the Precambrian era and the Cambrian period

• not present in living organisms

– Carbon-12 and carbon-14: calculate how long the organism’s been dead

• half-life of 5,730 years; only recent fossils

Continental Drift• Continental Drift:

motion of continents about Earth's surface on plates of crust floating on the hot mantle– North America and Europe

drifting apart at 2 cm per year– Explains how fossils are

similar on different continents– Pangaea- supercontinent

about 245 million years ago– climate change and

competition; extinction of species

Mass Extinctions

• Mass extinctions: brief episodes of great species loss– Cretaceous period, 65 million

years ago, extinction of dinosaurs• 1. Climate cooling and shallow

seas receding• 2. Meteor in the Yucatan; polluted

the sky with dust, blocking sun• 3. Rise of mammals

– Permian period; 90% of marine animal species

– Provide new opportunities for other species and new evolution

15.4 Taxonomy

• taxonomy: branch of biology that involves the identification, naming, and classification of species.

Linnaean System of Classification• Carolus Linnaeus

(1707 – 1778)• 1. binomial: two-

part Latin name for each species– first part is genus ;

first letter capitalized

– second part is species; all lower case

• ex. Homo sapien

• 2. hierarchy – broader to specific species– Kingdom– Phylum– Class– Order– Family– Genus– Species

• phylogenetic tree: a diagram that reflects hypotheses of evolutionary relationships with a branching pattern– greater the number of homologous structures, more closely

related

Convergent Evolution

• convergent evolution: process in which unrelated species from similar environments have adaptations that seem very similar

• analogous structures: similar adaptations that result from convergent evolution– ex. wings of insects and

birds; no common ancestor

DNA comparisons between species increase evidence of relationships

Cladistics• cladistics: method of determining

the sequence of branching• clade: each evolutionary branch

in a phylogenic tree– consists of ancestral species and all

descendants

• derived characters: all organisms in clade share homologous structures that do not occur outside the clade

• cladogram: a phylogenetic diagram that specifies the derived characters of clades– not always accurate because birds and

reptiles are similar

Classification Systems

• Old = 5 Kingdoms– Monera– Protista– Fungi– Plantae– Animalia

• New = 3 Domains– Bacteria– Archaea– Eukarya