5.1-5.4, 10.3 Diversity except 5.3 Flashcards
Evolution definition
Decent with modification definition
Heritable characteristics of a species changes over time
- Individuals with a phenotype that provides them with selective advantage
- Stay alive
- Reproduce
- More frequently pass on traits to next generation
- Traits increase in popularity
Mechanisms of evolution/changes in heritable characteristics
- Mutation
- 2 green parents end up with brown kid due to mutation - Genetic drift
- disappearance of particular genes by chance, some organisms die, do not reproduce - Migration
- Gene flow, e.g some brown beetles join population of gene beetles - Natural selection
- Selection pressure, struggle to survive
- Advantageous traits that confer selective advantage - live and reproduce, pass traits to offpsring, increase in gene frequency
Example of evolution (RWE) (essay)
Melanistic moths
- active at night, roost at day
- roost on tree bark
- unpolluted - bark is pale colour, coloured with lichens, moth is pale colour and peppered to camouflage
- polluted - So2 kills lichens, bark covered in soot, bark becomes black
- melanisitic (produce melanin) has selective advantage over pale as can better camouflage, lower chance of getting eaten.
- increase frequency of melanistic gene in polluted areas compared to unpolluted areas. Replaced peppered variety in polluted areas.
Evidence for evolution
Fossil
- evidence of different species in the past
- evidence species change over time
Artificial selection
- breed favourable traits, traits passed down to offspring
- evolution of crops (e.g. broccoli from wild mustard)
Homologous structures
- Same construction, different function due to different selective pressures in different environments
- Same ancestral origin
- Adaptive radiation
Homologous vs analogous structure
Homologous
- Same construction different function
- Same ancestral origin, become different because different environment has different selection pressure
- Divergent evolution by adaptive radiation
- Natural classification, follows evolutionary history, has predictive value
- Forelimb structure of animals
Analogous
- Same function, different construction
- Different ancestral origin, become same because same environment with same selection pressure
- Convergent evolution
- Artificial classification, does not follow evolutionary history
- Wings of bat and bird.
Adaptive radiation definition
Rapid evolutionary diversification from a common ancestor
- single species, different niche, different env conditions
- different selection pressures, adapt, develop diff morphological traits
Pentadactyl limbs
Homologous structure
Similar bone structure, 5-fingered limbs present in many amphibians, birds, mammals
- Crocodile - 4 limbs for crawling, hind limbs for swimming
- Penguin - hind limbs for walking, forelimbs are flippers
- Frogs - four limbs for walking, hind limbs for jumping
Divergence from a common ancestor via adaptive radiation, explains different function similar structure
How natural selection and evolution occurs
- Genetic variation due to meiosis, mutation, sexual reproduction
- Struggle for survival between individuals of same species - too much offspring and limited resources
- Selective advantage, favorable traits, more suitably adapted, get more resources, survive, reproduce, pass on traits. Less adapted die
- Pass on traits to offspring, increase in frequency of useful genes, decrease frequency of useless
- Cumulative change of heritable characteristics is evolution
Sources of variation
Mutation
- change in base sequence produce new alleles, enlarge gene pool
- mutagens/radiation
Meiosis
- crossing over, independent assortment
- new combinations of alleles
Sexual reproduction
- random fertilization
- allows mutations in parents to be passed on to offspring
Disruptive selection due to selective pressures
Transfer of genes between bacteria in plasmids
Adaptation definition
Characteristics that make an organism suitable to its environment
Development of antibiotic resistance
- multiple resistant bacteria
due to - overuse of antibiotics, low antibiotic dose when people dont finish treatment
- large bacterial population, higher chance of mutation
- high rate of reproduction
- pass genes on to each other via plasmids, transformation or conjugation
- random gene mutation - resistance
- gives bacteria greater antibiotic resistance
- antibiotic kill sensitive bac
- natural selection favor those with reisistance
- reproduce, increase allele frequency, pass traits to offspring
- resistance can be transferred between bacteria
- use different antibiotics but bacteria develop resistance also
- multidrug resistant bacteria
Definition of clade
How are members identified
Group of organisms from common ancestor
- Base sequences of gene or corresponding amino acid sequence of protein.
- Homologous structures
Use of mutations as a molecular clock
Mutations which cause change in AA sequence occur over long periods of time.
- occur at a roughly constant rate, can be used as molecular clock
- Positive correlation between no. mutations and time since divergence from last common ancestor
- Number of differences between species determined by how long a go species diverged
(assumption that only one mutation occurs at a time, possibility that a gene change may be large between closely related species, assumption of smallest possible mutations.
Cladogram explain
- Tree diagram showing most probable sequence of divergence in clades
- Based on base/AA sequences
- Computer programs calculate process of divergence, whilst minimizing changes in base sequene
- Branching points = nodes, hypothetical ancestral species that split
Define
Gene pool
Species
Allele frequency
All genes and different alleles in interbreeding population
Organisms that can interbreed to produce fertile offspring. Similar sequence of genes, phenotype, chromosome number
Measure of proportion of specific variation of gene in population, expressed as %
Reproductive isolation
Insurmountable barriers causing some members to be unable to reproduce
Allopatric speciation - occurs due to physical separation by geographic feature
- Geographic isolation
Physical barrier preventing male and females from finding each other
- interbreeding impossible, gene pool separated, speciation
Sympatric speciation - speciation despite population living in same area
Temporal isolation - populations mate/flower at different times/seasons, prevents gametes from meeting each other
Behavioral isolation
- one population’s lifestyle habits are not compatible with those from another. Eg Differ in courtship behaviour.
Define selection pressure
Types of selection pressures
Environmental factors act selectively on certain phenotypes resulting in natural selection.
Stabilizing selection - selection pressure removes extreme phenotypes
Disruptive selection - removes intermediate varieties
Directional selection - one phenotype favoured over the other. Frequency of one increase, other decrease
Polyploidy definition, advantage, disadvantage, example
Def: cell containing 3 or more sets of chromosomes due to non-disjunction
Advantage
- vigorous
- bigger fruits, more resistant to disease
Disadvantage
- Errors in replication
- instant speciation
Allium genus containing onions
- wild onion normal diploid number is 14, but there are some where diploid number is 28
Ideas about rate of evolution
Gradualism
- Evolution occurs slowly over long time
- changes are slow and steady
- Occurs when little change in environment
Punctuated equilibrim
- long periods of no change
- short periods of great change
- occurs when great changes in environment
How speciation occurs, definition of speciation
- Speciation def: splitting of species into 2 due to reproductive isolation
- Allopatric speciation - geographic, sympatric - temporal or behavioural
- Polyploidy can also cause gene pool separation
- Disruptive selection cause gene pools to diverge
- gradualism - small changes accumulate over a long period, punctuated equilibrium - large changes of short period.
- Species become too dissimilar, unable to interbreed to produce fertile offspring - speciation
Essay - natural selection leading to speciation
- Variation required for nat selection
- Sources of variation - meiosis, mutations, sexual repro
- Competition, struggle to survive
- Adaptations - some organisms are better adapted than others
- Reproduce, pass on genes, inheritance change in gene frequency
- Speciation - splitting of species into 2 species because of reproductive isolation
- Geographic, temporal, behavioural isolation
- Disruptive selection
- Gradual divergence of populations by natural selection
- Changes in gene pools of separated populations - interbreeding is impossible.
- Speciation
Variation - source - competition - adaptation - survival - inheritance
speciation - reproductive isolation - geog/temp/behavioural - disruptive selection - gradual divergence - changes in gene pool - no more interbreeding - speciation.
