IB Biology Topic 10: Macroevolution and Speciation

Directional selection

has the phenotypic distributed to two extreme phenotypes, ‘ two- hump graph.

Disruptive selection

has phenotypic distribution entirely towards one phenotypic extreme.

Fossil records

show abrupt changes in a species with periods of ‘ extinction that are perceived to be periods of stasis under the theory of punctuated evolution.

rapid bursts

Punctuated equilibrium= when speciation occurs in short, with periods of no change in between.

Low genetic variation

/diversity implies that if one organism of such a population is vulnerable to a disease, the entire population is also vulnerable.

Gene

pool= the combination of all alleles of a trait for a species.

meiosis

Occurs when does not occur correctly and the chromosomes are unable to be divided into two haploid gametes, and instead produce one diploid gamete by hybridization.

Behavioral isolation

= differences in mating behaviors that for two population.

Sympatric speciation

= occurs w /out a geographic barrier.

Temporal isolation

= differences in mating times for two different populations.

Speciation

is the development of different species.

Gradualism

= when speciation occurs gradually over time.

Species

= a group of organisms that can mate and reproduce and produce viable and fertile offspring.