Summaries of matric (CAPS) Life Science Evolution section.
Covers main points, and has steps for main subsections e.g. speciation. Includes comparison tables for Lamarck vs Darwin, natural selection vs artificial selection, apes vs humans.
evolution
intro
evolution + biological evolution
evolution - change
biological evolution - inheritable changes in populations of living organisms over time
population + species
population - group of organisms of the same species, living in a defined area at a particular time & able to
interbreed randomly
species - group of organisms w similar characteristics that are able to interbreed + will produce fertile
offspring
theories of evolution
lamarck
● law of use + disuse - organs become modified depending on how often it is used
○ used often - bigger/stronger
○ used less - gradually disappeared
● law of inheritance of acquired characteristics - modifications in parents are transferred to the
offspring
● rejected theory - lamarck believed in determinism (no evidence to show this); organisms did not
evolve bc they wanted to evolve, change happens randomly + in response to environmental stressor
darwin
● descent w modification - natural selection
○ most species produce many offspring
○ these species show much variation, some have suitable characteristics others do not
○ offspring compete w others for food, shelter, mates
○ only those w favourable characteristics survive
○ better adapted individuals survive better if environmental conditions change a lot - better
adapted will survive + find mates + pass on favourable alleles, next gen has more individuals w
favourable traits
○ natural selection + survival of the fittest
○ over many generations - population gradually changes
○ over long periods of time - population looks very different (phenotypically + genotypically)
○ process leads to development of a new species
lamarck darwin
theory of Inheritance of Acquired Characteristics / Natural selection
theory of Use of Disuse
change is voluntary involuntary
change is selected by the individual selected by nature
Individuals change because they choose to whole groups change in response to environment
changes = passed automatically to offspring changes = genetic + altered genes passed to
offspring
, natural selection artificial selection
nature selects which individuals change man selects which individuals to cross breed
change is slow change is much faster
change happens in response to environmental change happens as a result of human needs (profit +
changes productivity)
process has no cost expensive
after process, individuals are better suited to the may be worse adapted to the environment
environment
punctuated equilibrium
theory that species do not undergo gradual change overtime but exhibit periods of no change - stasis - after
which they undergo series of rapid changes splitting into several closely related species
no few/intermediate forms, PE explains lack of transitional forms in fossil records
speciation only occurs if there is an environmental stressor
variation within a population
variation caused by genetic differences
phenotype differences are caused by genotype differences - adaptive radiation (as they have a common
ancestor), all species will have ecological niche/role (birds that eat seeds vs insects)
diversification of a group of organisms from ancestral species into forms filling different ecological niches
caused by meiosis, mating, fertilisation
● meiosis
○ variation = introduced during prophase 1 - crossing over + recombination occurs
○ metaphase 1 + 11 when chromosomes place randomly on equator
● random mating
○ cannot be predicted - contributes to variation
● fertilisation
○ orgs form many gametes which are genetically diff from one another - exactly which sperm +
ova fuse cannot be predicted = variation
genetic mutations
random changes in genetic code may have following survival value
● some mutations have no effect on organism (neutral) (flower petals being different colours)
● some are harmful + kill organism (lethal) (plant is albino + cannot form chlorophyll)
● some are advantageous (fixed) (frog has longer legs)
discontinuous variation
caused by alleles of one gene or small amt of genes; individuals fall into distinct categories or groups (blood
types) - no intermediate forms (blood types)(bar graphs)
continuous variation
effects of many genes interacting, influenced by factors like diet - polygenic inheritance; wide range of
measurements (line graphs)(shoe size)
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