week 12, may 2nd - 6th Flashcards
Name and explain second condition for no evolution
No mutations
Mutations are changes in DNA
Singe nucleotide (added, substituted or removed) = usually would change codon on mRNA changing amino acid sequence
Crossing over = homologous chromosomes not exchanging the same amount of genes resulting in having an extra gene or missing a gene
Chromosome fails to separate properly during cell divisions resulting in adding or missing a chromosome
Name and explain third condition for no evolution
No migration
New individuals arriving or some individuals leaving would change gene pool
Name and explain fourth condition for no evolution
No selection of mates
Selecting a mate would change the frequencies of alleles or individuals in next generation
What did Lamarck say
Inheritance of acquired characteristics
Realized that the environment selected/ successful variant favoured
Believed that variations between individuals were acquired during lifetime and were found in offspring (false)
What did Darwin (Wallace) say
Theory of evolution = origin of species
Individual variants are inherited by genetics
Environment selects or favours the successful variant
More successful variants reproduce more
Next generation have more of successful phenotype
What is Darwin’s fitness
Number of offspring you produce that survive and are fertile
Name sources of variation
Mutations
Recombination of existing alleles by meiosis (crossing over and independent assortment), different mating pairs and migration
What is divergent evolution
Common ancestor structure evolved for different purposes
Structure called homologous
Different nice: ecological role
What is convergent evolution
Different ancestors evolved to form a common structure
Structure called analogous
Name the 3 trends of selection
Stabilizing selection
Directional selection
Disruptive selection
Explain stabilizing selection
Favours middle variant
Selects against both extreme variants
Ex = weight of baby at birth, clutch size (ideal amount of eggs laid)
Explain directional selection
Selecting one extreme
Ex = antibiotic resistance - bacteria
Pesticidic resistance - insects weeds herbicide resistance
Explain disruptive selection
Two types of environment
Each environment is selecting one of the extreme variant
Middle variant is selected against (killed)
Describe Batesian mimicry
Model is armed (poisonous)
Mimic looks like the model but is unarmed (palatable)
Like coral snake and king snake
Describe mullerian mimicry
Both model and mimic are armed
Predator avoids all of them
Like monarch and viceroy butterfly
Like wasps, bees and hornets
What are reproductive isolating mechanisms and name the two groups
Preventing two species from reproducing resulting in viable fertile offspring
Prezygotic barriers
Postzygotic barriers
Explain prezygotic barriers (5)
Prevents fertilization (zygote formation)
1 - habitat isolation (two species live in different places and therefore never meet (different continents))
2 - temporal isolation (different species, reproductive season is at different times)
3 - behavioural isolation (courtship ritual is species specific and doesnt attract different species
4 - mechanical isolation (different species of animals have different size and shape of genitals)
5 - gametic isolation (sperm of a different species cannot fertilize an ovum of another species because sperm has to bind to a species specific receptor
Explain postzygotic barriers (3)
Prevents formation of viable and fertile offspring
1 - reduced hybrid viability miscarriage (embryo or fetus dies before birth)
2 - reduced hybrid fertility (offspring is healthy but infertile like a mule)
3 - hybrid breakdown (offspring is outcompetes bu the two parental species)
What is speciation
Forming new species
Name the two types of speciation
Allopatric
Sympatric
Describe allopatric speciation
New animal species
Geographical barrier that fragments an original population into smaller populations that are prevented to reproduce together because the barrier isolated them from each other
With different mutations make them different species
Ex = Galápagos Islands, different species of tortoises
Describe sympatric speciation
New species of plants
New species originates within the two parental species range
Diploid set from both parents —> fertilization —> nondisjunction = new species
