chapter 2 Flashcards
principles of evolution by natural selection
- there is variation between individuals
sources of variation:
Age
Sexual differences
Environmental factors (differences of nutrition, disease, accident, etc.)
Individual difference in inherited traits
Most earlier natural historians believed in perfect types, and thought variation was degeneration from those types.
Darwin and Wallace documented that individual variation is significant, and the “perfect types” were just myths
- some of this variation is heritable
- reproduction capacity is much larger than survival of the offspring
- some animals have more descendants than others
fitness
Fitness: The proportionate contribution that an individual makes to future generations
Key points of natural selection:
Does NOT require simple things evolving into complex: sometimes a simplified mutation of a structure might be advantageous than the ancestral complex one
Can NOT evolve towards something with a goal in mind; only favors variations that are advantageous at the time of selection
human selection
Human selection: The breeding of selective traits in domestic animals and plants
Evolution within species
There is considerable variation within species
Some of this variation is heritable
e.g
Marine nudibranch (Elysia viridis): brown and green individual
Selection pressure
The environmental conditions that influence survival and reproduction of a species
e.g
Black and white Biston betularia against lichens and bare tree
Speciation
Speciation: The process in which a new species is formed from an initial one
Speciation ≠ evolution!
Is driven by natural selection
Is opposed by hybridisation
Can only occur when some sort of barrier prevents gene flow between two parts of a population (“Reproductive isolation”)
species
Species are groups of potentially or actually interbreeding natural populations that are reproductively isolated from other such groups
e.e defining is hard
Herring gull and lesser black-backed gull are two extremes of a spectrum
They can not reproduce, but the intermediate forms can
Founder effect
The composition of the pool of founder genes has a strong influence on the development of the population
Population bottleneck
An evolutionary event in which a large % of the population is killed or prevented from reproducing
e.g
In 1962/1963, almost all lobsters in the Oosterschelde froze to death
Today, Oosterschelde lobster is genetically distinct from North Sea lobsters
Oosterschelde lobsters are an isolated population
Larvae are carried north
Very little influx of larvae from the southern North Sea
Convergent evolution
Convergent evolution occurs when populations from very different ancestors have converged on very similar form and behaviour
e.g.
octopus and human eye
Parallel evolution
Parallel evolution occurs when populations long isolated from common ancestors follow similar patterns of diversification
Analogy
A similarity in form or function of a structure that does not result from common ancestry
Species richness
The number of species present in a community
Wallace
Cofounder of the theory of evolution alongside Charles Darwin (Alfred Russel Wallace)
Sexual selection
A form of selection that acts on an organism’s ability to obtain a mate
Malthus
Writer of the 1798 “Essay on the principle of population” (Thomas Malthus)
Mutualism
An interaction between individuals of two or more species in which both benefit in a reciprocal association
Beagle
Name of the boat on which Darwin sailed and developed his theory of natural selection
Allopatric
Occurring in different places, usually refers to geographical separation of species
Speciation
The process by which two or more new species are formed from one original species
Taxonomy
The study of the rules, principles, and practice of classifying living organisms
Coevolution
The process by which members of two or more species contribute reciprocally to natural selection pressures on each other, such as parasites and hosts
Species
The largest group of organisms in which any two individuals of the appropriate sexes can produce fertile offspring
Wegener
Founder of the theory of continental drift (Alfred Wegener).
Endemic
A species that is known only from one island or area.
Fitness
The contribution made to a population of descendants by an individual relative to others, and the relative contribution to the gene pool of the next generation.
Natural selection
The force that causes some individuals in a population to contribute more descendants and genes than others.
Hybridization
The production of offspring sharing characteristics from different lineages
Sympatry
The presence of two or more species living in such proximity that breeding should be possible but doesn’t usually occur
Homology
Similarity in structure assumed to result from common ancestry.
Marsupials
Mammals that have a pouch instead of a uterus.
Tadpole
Larval stage of a frog
Ring species
A species living in a situation where populations are connected by a geographic ring, allowing interbreeding (like the sea gulls)
Industrial melanism
A phenomenon in which black or blackish forms of species have come to dominate in industrial areas
Convergent evolution
The process by which organisms of different evolutionary lineages come to have similar form or behavior
