Biology Unit 8

The early atmosphere of the Earth was lacking in

Oxygen

Sequence of the origin of life

Abiotic synthesis of small molecules, then joining of small molecules into macromolecules, packaging of macromolecules into protocells, which are the origin of self-replicating molecules.

Protocell

Fluid-filled vesicles with a membrane-like structure; exhibit reproduction, metabolism, and the maintenance of an internal environment different from surroundings.

Stromatolite

Oldest known fossils; rocks formed from the accumulation of rocks on bacterial slime layers

Paedomorphosis

Retention of juvenile characteristics in the adult; change in timing of development

Heterochrony

Evolutionary change in the timing or rate of an organism's development

Allometric growth

Varied rates of growth for different parts of the body

Adaptive radiation

The diversification of a group of organisms into forms filling different ecological niches

How can newly formed volcanic islands lead to adaptive radiation?

The clean slate of new islands, and lack of previous selection pressures, leads to adaptive radiation

Endosymbiosis

A theorized process in which early eukaryotic cells were formed from small prokaryotes living in host cells

Evidence for endosymbiosis

Mismatched membranes, mitochondrial DNA, correct sizes and shapes of prokaryotes

Biological species concept

States that, "for a population to be declared a separate species, it must have diverged significantly from other populations"

What must happen for a group of organisms to be classified as a different species?

Reproductive isolation

Prezygotic isolation

Prevent mating or fertilization; includes temporal, habitat, geographic, behavioral, mechanical, and gametic isolation

Postzygotic isolation

Reproductive failure after fertilization; includes reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown

Temporal isolation

Mating at different times; ambient temperature may play a role

Habitat isolation

Different habitats in the same area

Geographical isolation

Completely different areas; the cause for allopatric isolation

Behavioral isolation

Difference in required courtship behaviors

Mechanical isolation

Incompatible genital organs

Gametic isolation

Incompatible egg and sperm

Reduced hybrid viability

Impairs the hybrid's development and survival in its environment

Reduced hybrid fertility

Problems during meiosis cause abnormal gametes

Hybrid breakdown

Some first generations are viable, but when they mate with one another or parent species, offspring of the next generation are feeble or sterile

Allopatric speciation

Geographically separated populations subsequently undergo genetic drift or natural selection

Sympatric speciation

Divergence of two populations in the same geographic region

Allopolyploid

Hybrid with multiple sets of chromosomes from two species

Autopolyploid

Hybrid with multiple sets of chromosomes from a single species

Puncuated equilibrium

Long periods of stasis punctuated by periods of rapid speciation triggered by environmental changes

Gradualism

Continuous evolution over long periods