Unit 4 Biology AOS 2 SAC 5 preparation

Evolution

Evolution

The gradual change in a species over time

natural selection

the principle that, among the range of inherited trait variations, those contributing to reproduction and survival will most likely be passed on to succeeding generations

selection pressure

the environmental factors that favour certain phenotypes

artificial selection

Selection by humans for breeding of useful traits from the natural variation among different organisms

survival of the fittest

Process by which individuals that are better suited to their environment survive and reproduce most successfully

gene pool

Combined genetic information of all the members of a particular population

Allele Frequencies

the relative abundances of alleles of a given gene among all individuals of a population

Hardy-Weinberg equilibrium

condition that occurs when the frequency of alleles in a particular gene pool remain constant over time

Gene flow

movement of alleles/individuals from one population to another

genetic drift

A change in the allele frequency of a population as a result of chance events rather than natural selection.

bottleneck effect

A change in allele frequency following a dramatic reduction in the size of a population

founder effect

change in allele frequencies as a result of the migration of a small subgroup of a population

Mutation

A change in a gene or chromosome.

frameshift mutation

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

Deletion (point mutation)

nucleotide is removed from the DNA sequence

Insertion (point mutation)

when one nucleotide is added to the DNA sequence

substitute (point mutation)

when one nucleotide is changed to another in a DNA sequence

Inversion (block mutation)

reversal of a section of DNA on a chromosome

Insertion (block mutation)

A section of DNA is added to a chromosome

deletion (block mutation)

removal of a section of DNA to a chromosome

Translocation (block mutation)

switching of two sections of DNA on different chromosomes

Fossilisation process

1. Organism dies quickly, covered and undisturbed
2. Sediments cover the body to decrease oxygen to stop bacterial decompositions
3. Bones start disintegrating but minerals replace hard tissue
4. Erosion occurs exposing the fossil, and someone finds the fossil

Fossilisation requirements

die in water, covered quickly by sediment, hard body parts, left undisturbed, lack of oxygen

trace fossil

a fossil of a footprint, trail, burrow, or other trace of an organism rather than of the organism itself.

Physical fossils

Remains of all or part of the structures of an organism

transitional fossils

fossils that show links in traits between groups of organisms used to document intermediate stages in the evolution of a species.

Biosignatures

Chemical or physical traces that can be inferred to have resulted from the action of life forms; indirect evidence of life.

relative dating

Method of determining the age of a fossil by comparing its placement with that of fossils in other layers of rock

Index fossils

Distinctive fossils used to establish and compare the relative ages of rock layers and the fossils they contain

stratigraphic method

the method of obtaining the relative age of an object by its position within a given sequence of rock strata

Absolute dating

A technique used to determine the actual age of a fossil

half-life

length of time required for half of the radioactive atoms in a sample to decay

Parent isotope
Daughter isotope

- isotope that undergoes decay
- Product of this decay

missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

silent mutation

A mutation that changes a single nucleotide, but does not change the amino acid created.

homologous structures

structures that are similar in different species of common ancestry but have different functions

vestigial structures

remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species.

analogous structures

Body parts that share a common function, but not structure

comparative embryology

the study of the similarities and differences in the embryos of different species

molecular homology

similar amino acid sequences or DNA sequences among different species from a common ancestor; evidence of common ancestry

phylogenetic tree

A family tree that shows the evolutionary relationships thought to exist among groups of organisms

Relatedness

The probability that two people share the same genetic information from a common ancestor.

common ancestor

An ancestral species from which later species evolved

speciation

Formation of new species

allopatric speciation

The formation of new species in populations that are geographically isolated from one another.

Galapagos finches

-The 19 islands served as a geographical barrier preventing gene flow; there are 18 known species of the finches;

- they have a vast array of beak shapes and sizes tailored towards species food sources on the different islands

- it is hypothesised changes have occurred largely due to allopatric speciation

- Often food source selection pressure

- Prevents gene flow

adaptive radiation

the diversification of a group of organisms into forms filling different ecological niches.

sympatric speciation

The formation of new species in populations that live in the same geographic area through reproductive isolation

Howea Palms

the two species H. forsteriana (lives in both soils) and H. belmoreana (only grows in volcanic soil). The palms have different flowering times; the difference in soil acidification is hypothesised to be the catalyst for the speciation

A difference in flowering times occurred; becoming a reproductive isolating mechanism; as the differences accumulated, the two species of palm could no longer interbreed to produce viable and fertile offspring