Glossary of Biology:Evolution

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Gene Duplication
-occurs in cell division when the chromosomes do not crossover equally.

-this causes more than one copy of the gene to be inserted into the genome.

-this DNA creates duplicate copies of genes that at first are useless but are susceptible to change and

-these copies of genes can be altered and create “gene families” that have similar structures but a slightly different functions.

Genetic Drift
-genetics can measure how frequently an allele shows up in a population

-allele frequency

-when the allele frequency changes as a result of chance this is called genetic drift

ex: 5 in a population of 50 frogs can carry an allele for white spots. If severe weather wipes out half the population we might find that all drogs with the white spot allele dies. This would cause the inheritable trait to disappear. If they survive the white spot allel could become more frequent

Artifical Selection
-selective breeding

- selecting offspring of organisms with desirable traits and breeding them

-those with more desriable traits would survive

-structures that share a common origin but different function

-similar bones in similar positions

ex: human hands are for grasping, moles claw are for digging

-structures that are similar in function but have no shared origin or anatomy

ex: wings of birds and bees are not similar in structure but serve the same purpose

-structures that serve no useful function

ex: wisdom teeth

Evidence for Evolution
-fossil records

-radiometric dating(half-life)

Erasmus Darwin

-all life may have a single source

Chevalier Lamarack

-environment plays a key role in evolution

Theory of Acquired traits: changes acquired as a result of adaptation to the environment conditions could be inherited by future generations

Theory disproven: environment can drive evoluation but acquired traits can\'t be inherited

Charles Darwin

-natural selection
George Buffon

-species could change over time and these species create new ones

Sir Charles Lyell


-the earth underwent and continues to undergo slow gradual change

-erosion, sedimentation

Radiometric Dating

-radioisotopes are atoms that give off radiation as they break apart or decay

- the rate of decay can be measured accurately

- time required for a quantity to fall to it\'s half life as measured at the beginning of the time period

ex: Uranium from 204g to 102 in 713 million years

Stabilizing Selection

-occurs when most common of the traits (allels) in a population are favoured by the environment

ex: most babies are born weighing a bit over 3kg. Babies under this can develop mental premature and risk death. Those over this often suffer birth trauma

Insertion or Deletion Mutation

- part of the DNA code is deleted or a new code is inserted. Mostly harmful

Sexual Dimorphism

-striking difference in gender
Sexual Selection

-the selection of any trait that favours a trait that will improve the mating success of an individual

Disruptive Selection

-occurs when individuals with traits of opposite extremes are favoured. The environment may favour more than 1 trait

Directional Selection

-occurs when the environment favours more extreme variation in a population. This can happen when organisms migrate to a new habitat where they encounter new forces of selections

ex: the peppered moth changing to melanic moths after pollution covered trees with black soot

Cumulative Selection

- allows the more complex traits to evolve

ex: stages of eye complexity in mollusks

-evolutionary formation of a new species

-when changes occur in a psecies this is called microevolution

-occurs when there are changes in the allele frequency and traits of a population within a species

Reproductive Isolating Mechanisms

-any behavioural, structural or biochemical trait that prevents organisms (of different species) from successfully reproducing

Ecological Isolation

-organisms of different species live in different habitats to prevent breeding

ex:woodchuck is closely related to the marmot but they live in different fields

Temporal Isolaton

-organisms are reproductively mature at different times

ex: plants bloom in different seasons

Behavioural Isolation

-organisms have distinct mating rituals to attract organisms of the same species

ex: male jumping spiders may not attract different species of female spider

Mechanical Isolation

-a structural difference in reproductive organs that prevents intercourse

-ex: shape of anthropod\'s penis are different even if species are closely related

Gametic Isolation

- the prevention of fertilization

-sperm and eggs of different species do not recognize each other

Zygotic Mortality

-no zygotes or embryos mature

Hybrid Inviability

-hybrid offspring are unlikely to live long

Hybrid Infertility

-hybrid offspring are sterile(mule)

Natural Selection

-all species have inherited variations of taits

-those with more favourable traits will produce more offspring that are likely to survive

-these traits will be passed on to future generations

Genetic Variation

-genes are located at certain positions or(loci) on chromosoms

-genes come in different forms called allels

ex:you may have brown eyes but you might carry a gene for blue eyes

Neutral Mutation
-one that has no effect on the reproductive success of an individual

Harmful Mutation

-one that reduces the reproductive success of an individual, causing gene malfunction and affecting cell division

Beneficial Mutation

-one that increases reproductive success causing improvement in gene function

Point Mutations

-can cause a neutral mutation if it occurs in an non-coding area of the DNA

-can cause harmful mutations if it occurs in coding area and affects it negatively

-can cause benefical mutation if it occurs in a coding area and affects it positively

Behavioural Changes

-differences among male and females

-evolution of populations into separate species as a result of being geographically separated (founder)

-evolution of a new species within the same geographic location. Genetic variation can cause an immediate reproductive isolation and a new species is created.

Adaptive Radiation
-rapid evolution

- occurs when one species of organism (ancestral species) rapidly forms a variety of species that are all adapted differently

-key adaption: evolves to avoid competition (specialization)

Endosymbiotic Hypothesis

-How the eukaryotic cell came into existence

-Mitochondria are the result of endocytosis (a cell engulfing something) of aerobic bacteria

-Chloroplast are the result of endocytosis of photosynthetic bacteria

-Aerobic bacteria and the photosynthetic bacteria were engulfed by large anaerobic bacteria

-This arrangement became a mutually beneficial relationship (Symbiotic)

Bacteria and Antibiotic Resistance

-plasmid in bacteria can contain enzymes that are resistant to antibiotics.

-bacteria that do not have this will die off

-stronger bacteria will conjugate and pass off the enzyme in the DNA

-resistance is good for bacteria, but bad for us

- similar traits arise in species because each species has independently adapted to similar environments

- occurs when species that were once similar to an ancestral species become increasingly distinct.

- 2 species are dependant on one another to evolve. Species put selective pressure on one another so they evolve together.

ex: bees and flowers

Bottleneck Effect
- when only a very small pool of alleles survive a dramatic event and a new population is established

Founder Effect
- when few individuals in a large population leave to establish a new population

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