REVISION Flashcards
(27 cards)
Define variation
the range of phenotypes in an offspring. This due to a variation in genes
What are the three types of variations?
- Mutations
- Independent assortment: different combinations of chromosomes
- Recombination or crossover
What is natural selection?
Individuals with certain characteristics are better adapted to a particular environment and thus survive to pass on these genes
What are selection agents?
Abiotic or biotic factors that influence survival
Define evolution
change over time into a different species
Define a species
A group of closely related organisms that are very similar to each other and are capable of interbreeding and producing fertile offspring
List some Biotic factors:
Predators, disease, competition, availability of food
List some abiotic factors:
heat, cold, wind, availability of oxygen and water, pH of soil and water, living space
List the four main pieces of evidence for support of evolution and briefly explain them:
- Fossil evidence: fossils found that look like organisms that live today
- Biogeography: distribution of animals and the concentration of similar types of animals in certain places on earth
- Comparing embryos: similarities between different animals embryos is observed. Particularly evident in vertebras.
- Comparative DNA: chimps and humans share 96.2% of their DNA which supports that they have a common ancestor
Define convergent evolution:
Different animals from different evolutionary paths that have similar features due to adaptions to a similar environment. for example sharks and dolphins.
Define divergent evolution:
Physical features of a common ancestor change overtime to perform different functions in different environments
Define analogous structures:
Body parts that do the same job, however, are made up of different parts
Define Homologous structures:
Body parts made of the same thing or from a common ancestor, however, do a completely different job or have a different function
Define Reproductive Isolation:
When species are isolated by barriers which prevent interbreeding
List and define some Prezygotic Isolation Mechanisms:
- Physical Barriers: mountains, rivers, oceans, ice sheets, deserts
- Temporal Barriers: mating seasons, nocturnal
- Habitat Barriers: ground or tree-dwelling, forest or grasslands
- Behavioural: mating calls, rituals, dances and body language displays, courtship rituals
- Gamete morality: sperm not being able to survive in the reproductive tract of another species
- Structural barriers: shape and size of mating organs
List and define some Postzygotic Isolation Mechanisms:
- Hybrid Sterility: offspring produced is sterile
- Hybrid Inviability: offspring produced is not viable in womb and dies while mother is pregnant
- Hybrid Breakdown: Second generation of hybrid offspring infertile or inviable
- Hybrid Availability: lack of fellow hybrids to continue reproduction
List differences between primates and humans:
- cognition and thought
- amount of hair
- bipedalism
- speech
- chin bone
- canine teeth size
- S-shape or C-shape spine
- Opposable big toe
- the ratio of legs to arms
Define Hominid:
the group consisting of all modern and extinct great apes.
Define Hominin:
the group consisting of all modern and extinct human species and all immediate ancestors of human
Outline the basis of the Multiregional Hypothesis for Human evolution:
Human ancestors left Africa and the modern Homo sapiens emerged gradually throughout the world and as the populations dispersed they remained in ‘genetic contact’
Outline the basis of the Replacement Hypothesis for Human evolution:
Also known as the ‘Out of Africa Hypothesis’. Homo sapiens developed as a separate species in Africa, then these completely modern humans spread around the globe, replacing the archaic populations (Neanderthals) when they came in contact
Define Race
A subdivision of a species where gene flow is possible
Define Allopatric evolution
Different houses in different areas to live in
Define Sympatric evolution
Same houses in same areas to live in
