Members of a population that have the ability to breed with each other under natural conditions, producing offspring that can reproduce
Prezygotic isolating mechanisms
Ecological: occupy different habitats
Temporal: breed at different times
Behavioural: give wrong mating signals
Mechanical: parts wont fit
Gametic: gametes won't join
Postzygotic isolating mechanisms
Zygotic mortality: zygote dies
Hybrid invariability: it doesn't live long
Hybrid infertility: it is infertile
Modes of speciation
Allopatric Speciation: speciation as a result of geographicalisolation
Sympatric Speciation: evolution of populations within the same geographical area into separate species
Most common mode of speciation is from geographical isolation
Darwin's theory of evolution by natural selection explains how species change over time through the accumulation of small genetic changes (mutations) and selective pressures from environmental factors.
Divergent Ecolution: 2+ species evolve increasingly different traits
Convergent ecolution: 2 or more species bome increasingly similar in phenotype in response to selection pressures
Adaptive Radiation: divergent evolution occuring so fast that 1 species gives rise to 3+ species
Coevolution: 2 species that are totally dependant on each other for survival, and therefore evolve together
homologous features: same origin, different functions now
analogous features: similar in funciton but not in origin
vestigial features: non-functioning structures homologous to functioning structures in related species.
Darwin's postulates
Many more are born in each generation than will survive and reproduce
There is variation among individuals
Individuals with certain characteristics have a better chance of surviving and reproducing than individuals with other characteristics
At least some characteristics resulting in differential reproduction are inheritable
Enormous spans of time were available for slow change
Darwin sailed on the HMS Beagle along the South American coast
1831
Darwin's role
Captain's mate, became the naturalist
Darwin published 'On the Origin of Species by Means of Natural Selection'
Lamarck
Organisms respond to felt needs
Characteristics acquired by an individual during its lifetime
Are transmitted to their offspring
Characteristics of each generation
Would be by all that happened to the members of the preceding generation