Lecture 9 Flashcards
what is microevolution
- NS
- migration
- mutation
- genetic drift
it is the little issues to the population
what is macroevolution
the process of microevolution explain macroevolution
- speciation, extinction, history, evolution of species
why is there a problem with defining the definition of a species
there are many species concepts and there is different ways to express
- genetic, biological, Darwinian, evolutionary, phylogenetic, ecological
the two MAIN species concepts are taxonomic (morphological) and biological
define taxonomic/morphological species concept
based primarily on distinct measurable differences
- species defined as a group of organisms that are sufficiently similar in phenotype (darwin also approved)
define the biological species concept
a group of interbreeding natural populations that are reproductively isolated from each other’s groups
(when 2 different species stop sharing alleles and become isolated within reproduction)
- focuses on the process of divergence
- DOES NOT apply well for bacteria, asexuals, self-fertilizing species, fossils
T/F reproduction is key to distinguishing species
true
what are the 2 types of speciation
- allopatric
- sympatric
explain allopatric speciation
- occurs when a population is geographically separated (mountain, river, etc) into 2 or more groups
- no gene flow
- overtime the genetic differences = too much = speciation
what is sympatric speciation
- not physically separated
- reproductive isolation arises from behavioural, ecological, or genetic differences within the same environment.
- this can begin to occur within an environment thru disruptive selection, behavioural selection (mate preference), different feeding habits
at what stages can reproductive isolation occur
finding a mate
fertilization
development and growth of F1 generation
adult survival
reproduction of F2 generation
what is included in pre-zygotic barriers
- finding a mate
- fertilization
geographic, temporal, behavioural, mechanical, gametic - also known as cellular (prevents the formation of a zygote - prevention of mating)
what is included in post-zygotic barriers
- development of zygote - F1
- adult reproduction - F1
- survival/growth/reproduction - F2
- Prevention of the offspring to become a viable fertile adult
- inevitability, sterility, hybrid breakdown
what is an example of pre-zygotic temporal isolation (from lesson 9)
apple maggot flies
- there are different timings of fly mating on the preferred host plant
the apple’s reproductive time is earlier than the flies
- different flies have different mating times - meaning that they cannot = gene flow
what is an example of pre-zygotic mechanical isolation from the lesson
the binding of the protein in the lysin sperm could not fertilize the egg because there was different evolutionary changes in different species
what are the 2 types of post-zygotic barriers
- intrinsic
- extrinsic
what do intrinsic post-zygotic barriers mean
- barriers that are due to internal factors that are not related to the environmental factors
inviability, sterility, or abnormal development of hybrids after fertilization - F1 generation has these problems
what do extrinsic post-zygotic barriers mean
barriers due to the external/environmental factors that affect the survival/reproduction ability of the hybrid
- hybrids may survive but lack the adaptions that are needed to survive (this can occur behaviorally/ecologically)
- makes them less successful than the parental generation
what is an example of intrinsic post-zygotic isolation
the mule
- it is a sterile hybrid that cannot create offspring
(male donkey x female horse)
the hinny
female donkey x male horse
sterile hybrid
- these examples affect the F1 generation (F2 not possible)
what is genetic distance
it is the measure of the degree of genetic differentiation between samples
- as genetic distance increases, post-zygotic isolation increases (more differentiation between F1 and parental = less fit = intrinsic isolation)
what is an example of extrinsic post-zygotic isolation
- poorly adapted butterflies
- the offspring was created with very bright wings = high risk of predation = higher mortality and lower mating success = very unfit
- there is a strong selection of lighter-coloured wing patterns - so the hybrids having bright colours is not favoured = extrinsic
what is adaptive radiation
- a single ancestral species rapidly diversifies phenotypically and ecologically into multiple new species, each adapted to a different ecological niche or environment
- driven by NS
- originates from a single common ancestor
- the species differ a lot in traits - ie. Galapagos finches
what is adaptive EVOLUTION
changes to the gene pool of a population which continuously improves the survival and reproduction of the organism as it becomes more popular among the population
is local adaptation needed for speciation
it is not necessary but it accelerates population divergence and the evolution of reproductive isolation
- sometimes divergence can occur from genetic drift, founders effect, behavioural isolation
- BI: cichlid fish = different mate preferences - sympatric speciation - new species can evolve in the same habitat because of selective mating
explain the example of the 3-spined stickleback fish in freshwater vs marine and how it relates to local adaptations
in freshwater, there are fewer predators meaning that they don’t need their armour
in marine, lots of predators = bony armour needed
this local adaptation is created because of the fitness of the environment - this can generate selection for reproductive isolating mechanisms
why do organisms diverge and become distinct species
when pops genetically diverge it is because of evolutionary forces - microevolution (genetic drift, mutation, NS, barriers)
- becoming reproductively isolation is a by-product of the evolutionary changes within a population
what 4 features commonly identify an adaptive radiation
- recent common ancestry of a single species
- phenotype-environment correlation (adaptions based on different environments)
- trait utility - actively using the new trait
- rapid speciation
what causes adaptive radiation
- Ecological opportunity is the absence of competition for resources. When new or previously unavailable ecological niches open up, species can exploit them and diversify rapidly.
- what triggers the exploitation is major changes such as colonization (new regions to explore and adapt to), extinction (eliminates big competitors from the prey to thrive in), climate change/natural disasters, the evolution of a trait that provides access to new resources (increase fitness in lizards after evolving toepads)
- high potential/tendency for speciation
- reproductive isolation is more readily common in some clades than others (finches and mockingbirds)
what is hybridization
when 2 different species = offspring = hybrid
- common in plants and fish
- can result in complex patterns of variation
- can be evolutionary significant for speciation
what is polyploidy
when an organism, tissue or cell has more than 2 complete sets of homologous chromosomes (humans have 3, others may have 3,4,5…)
what is allopolyploidy
- the most common type of polyploidy is allopolyploidy
–> a duplicated complete set of chromosomes after hybridization between species (2 or more species) - often fertile - wheat is an allopolyploidy because it contains chromosomes from 3 different types of grass
what is autoploidy
arises from a duplicated complete set of chromosomes (karyotype) WITHIN a species (more than 2 sets of chromosomes from one single species)
how does hybridization form an allopolyploid
- two species mate = F1 hybrid (AA)
- F1 hybrid produces diploid gametes (meiotic nondisjunction - error that doesn’t separate the pairs of chromosomes)
- diploid gametes produce tetraploid F2
- tetraploid zygote is fertile but is reproductively isolated from parental species
(a form of sympatric speciation)
what is the evolutionary significance of polyploids
- their inability to reproduce with parental generation
- they allow the exploitation of new habitats
- have improved growth and development than parents because of heterozygosity
- a lot of the flowering plants = polyploids
