evolution Flashcards
what is evolution
process of genetic change in a population over time
Jean Baptiste Lemarck
-Inheritance of acquired characteristics: passed on to its offsprings
-Use and Disuse: body parts not used would be lost and disappear
-THEROY: giraffe’s long neck
Giraffes stretched necks to eat from tall trees, this trait passed onto generations
Charles Darwin
-Travelled on HMS beagle, mapped South American Coast
-Explored regions and collected samples (plants, animals, rocks, fossils) (flora and fauna)
-Some animals of extinct animals looked similar to living animals
-Animals on Galapagos Islands resembled animals observed on South American Coast
what is an adaptation
structure, behaviour, or physiological process that helps an organism survive and reproduce in a specific environment
structural adaptation
physical features
ex: camouflage, mimicry, webbed feet
- mimicry: resembles a harmful species
- camouflage: allows organisms to blend with surroundings
physical adaptation
internal and cellular features that helps them to survive in environment
ex: toxins produced by plants
behaviour adaptation
actions of organism that helps them to survive in environment
ex: hibernation, birds migrating south
-hibernation: reduce metabolism to save energy and survive harsh winters
ex: ground hog
what is natural selection
process of change in the characteristics of a population of organisms over generations
what is artificial selection
describes changes to a population caused by selective breeding by humans
Ex: cats bred for appearance
what is sexual selection
natural selection for mating based on competition between males and choices made by females
what are some of the historical contributions that led to the idea of evolution
- animals observed on the Galapagos Islands resembled animals observed on the South American coast by Darwin
- discovery of fossil bones from large extinct mammals
peppered moth study
- would camouflage in trees covered in lichen, prey for birds
- air pollution from new factories killed the lichen and soot covered the trees
- moths that survived long enough to reproduce were able to pass on genes to their offspring
what is a population
consists of all the members of a species that live in an area at a certain time
what is allele frequency
number of times an allele occurs in a gene pool compared to the number in the pool for the same gene
what is gene flow
net movement of alleles from one population to another
what is genetic drift + the two types
changes in allele frequency due to chance events
- FOUNDER EFFECT: individuals start and establish a new isolated population
ex: galapagos islands
- BOTTLENECK EFFECT: change in gene pool resulting from rapid decrease in population size
ex: elephant seals due to overhunting
what are the three types of natural selection (know graphs)
- STABILIZING SELECTION: favours intermediate phenotypes and acts against extreme phenotypes (narrower range)
- ex: babies birth weight - DIRECTIONAL SELECTION: favours phenotypes at one extreme over another, results in shifted range of phenotypes
- ex: peppered moths - DISRUPTIVE SELECTION: favours both extremes rather than intermediate phenotypes, results in split gene pool
- ex: african finches
(know graphs for each)
analogous vs. homologous structures
ANALOGOUS: similar structure but may have different functions
ex: vertebrate forelimbs in birds, whales
HOMOLOGOUS: similar function but different structures
ex: birds and bats
what is speciation
macroevolution vs. microevolution
MACRO: changes occur over long period of time
MICRO: change in gene frequencies within a population over time
pre-zygotic mechanisms
prevention of mating
1. BEHAVIOURAL ISOLATION: behaviour that prevents interbreeding with closely related species
- ex: mating rituals
2. HABITAT ISOLATION:s pecies in same area occupy different habitats, rarely encounter each other
- ex: garter snakes in water and meadows
3. TEMPORAL ISOLATION: species kept separate due to timing barriers, mate at different times (seasons, years, etc.)
- ex: flowering
prevention of fertilization
4. MECHANICAL ISOLATION: related species anatomically different, can’t mate
- ex: variations in flower structure prevent pollination
5. GAMETIC ISOLATION: sperm can’t reach or fertilize egg
- ex: plants may land on stigma- fertilization doesn’t occur
post-zygotic mechanisms
- HYBRID INVIABILITY: develops but can’t survive to maturity
- ex: cotton plants- produce weak and sterile seeds - HYBRID INFERTILITY: two species can mate but hybrid is sterile and can’t reproduce
- ex: horse (female) and donkey (male) -> mule (sterile) - ZYGOTE MORTALITY: genetic differences may stop development of zygote
- ex: sheep and goat hybrids -> fertilization occurs but zygote doesn’t survive
allopatric speciation
populations separated by a geographical barrier and diverge genetically
ex: lava flow, water
sympatric speciation
populations within same geographical area diverge genetically
ex: polyploidy- results in extra chromosomes due to error in cell division
adaptive radiation
diversification of a common ancestral species into a variety of differently adapted species
ex: galapagos islands
divergent evolution
occurs when populations adapt to different environmental conditions, diverge and become distinct
- common ancestor
ex: adaptive radiation
convergent evolution
occurs when unrelated species occupy similar environments in different parts of the world
- no common ancestor
ex: birds and bats have wings
gradualism hypothesis
small, adaptive changes gradually accumulate over time
- fossils rarely reveal gradual transition
punctuate equilibrium hypothesis
interrupted by periods of divergence
- supported by fossil evidence
