Studied by 20 peoplePolyploidization
a process by which an individual is formed with extra sets of chromosomes
Autopolyploids
spontaneous genome duplication within a population
Allopolyploids
genome duplication in association with hybridization between 2 different species
What is Sympatric Speciation?
speciation that occurs without geographic isolation (microhabitats)-think of a species evolving within another species population (due to factors like preference for different habitats and fruit (soapberry))
What occurred in the Soapberry Fruit Fly?
-disruptive selection due to assortive mating in beak length related to fruit size availability (native fruit = long beak, non-native fruit = short beak)-is an example of sympatric speciation because there was not physical isolation when the species diversified, just isolation in preference
Why can't triploid individuals reproduce?
since they rarely contain the same # of chromosomes, offspring would be produced with an uneven (dysfunctional) distribution of chromosomes
Adaptive Introgression
when advantageous genetic variation is transferred between species
Homogenization
when genetic differences between 2 populations become less distinct due to interbreeding-caused gene flow
Reinforcement
if 2 populations are extensively diverged, their hybrid offspring may have a lower fitness (disfavours hybrids)-refers to the selection of traits that isolate populations reproductively-basically post-zygotic isolation
Assortive Mating
when species find partners based on their similarity to each other
Homology
similarity resulting from common ancestry
Homoplasy
similarity for reasons apart from common ancestry
The Cladistic Approach
estimating a phylogenetic tree based on synapomorphies
Synapomorphies
a shared derived character trait which only those in a specific clade contain
Maximum Parsimony
assumes that the best explanation is often the simplest one that implies the least amount of change
Hox Genes
series of genes that controls that defines what section of the body is what
Transcription Factors
influence expression of other genes (e.g. a Hox Gene)
What is that difference between Hox genes and Downstream Genes?
Hox genes are responsible for defining what each section of the body is, other genes orchestrate what structures form in that part of the body
Homeobox Domain of Hox
a 180-bp DNA binding domain that all Hox genes have (but not all genes with a homeobox are hox)
Evidence related to DNA sequence that explain why Fruit Flies and Humans are Homologous?
we both share similar DNA sequence (including homeobox domain)
Evidence related to genomic organization that explain why Fruit Flies and Humans are Homologous?
we both share similar genomic organization
Evidence related to development/expression patterns that explain why Fruit Flies and Humans are Homologous?
we both share similar expression patterns during development
Evidence related to other species that explain why Fruit Flies and Humans are Homologous?
other species closely related to fruit flies and humans also have Hox genes with these features
What does SINE represent?
S: shortI: interspersedN: nuclearE: elements
What is an artiodactyl? (in relation to Whippo Hypothesis)
an ankle bone
What was the old theory regarding cladograms and the Whippo Hypothesis?
originally, whales were placed outside of a proposed monophyletic mammal group containing the synapomorphy artiodactyl (ankle bone)
What did data show in relation to SINEs and the Whippo Hypothesis?
-whales (originally outside the clade) and hippos (inside) share many SINEs that are absent outside of the proposed artiodactyl synapomorphy group
What does a relation in SINEs mean for the Whippo Hypothesis?
they indicate that whales and hippos share derived traits and support the Whippo Hypothesis (whales and hippos are closely related)
What is the Whippo Hypothesis?
the hypothesis that whales are most closely related to hippos and split off from a common ancestor
Atavism
an ancestral characteristic that was lost but then re-emerges during evolution
In Situ Diversification
diversification from a single ancestor within a single habitat-a component of adaptive radiation
Ecotypes
populations with adaptions to unique environments
Adaptive Radiation (2)
-an evolutionary pattern where many species evolved from a single ancestor within the same space-rapid diversification accompanied by ecological (in situ) diversification
What is Adaptive Radiation triggered by?
-Biological Innovation-Ecological Opportunity
What is Biological Innovation in relation to Adaptive Radiation?
when a new gene/mutation gives a species an advantage to survive (ex. extra limbs, exoskeleton)
What is Ecological Opportunity in relation to Adaptive Radiation?
an exploitation of a new resource or a habitat
What can cause Ecological Opportunities? (2)
Colonization; a new habitat can be an eco. opportunityCompetition: the extinction of a species can open a new niche of other species
Frog Diversity in Philippines vs. Sulawesi (Ben Evans Study)
-the Philippines a more consistent diversity than Sulawesi-diverged species evolved on Sulawesi due to opened ecological opportunities (fast-moving water = large froggie, no water = small froggie)
Null Hypothesis of Ben Evans Study on Sulawesi
there was no adaptive radiation on Sulawesi-meaning that different sized frogs evolved elsewhere and then came to Sulawesi rather than the adaptive radiation of a single frog evolving in situ (diversification in a single habitat)
Findings of Ben Evans Study on Sulawesi (2)
-that a frog dispersed to Sulawesi and through adaptive radiation, evolved into 3 different ecotypes which then diversified multiple times-species on Sulawesi are sympatric as they speciated due to preference for different habitats
How is the Cichlid Fish an example of Adaptive Radiation?
they have functionally decoupled set of jaws (oral and pharyngeal) which specialize in food collection and processing allowing for the exploitation of new niches
Background Extinction (3)
the level of extinction when mass extinctions are not occurring (1 species per 1mil per year)can be due to:-normal environmental change-diseases-competition
Mass Extinction
a large amount of biodiversity is lostcan be due to:-extraordinary or sudden changes within an environment
What is the Impact Hypothesis?
That 65mya, a meteorite struck and caused 60-80% extinction
Differential Survival
individuals best adapted to existing conditions tend to survive more and reproduce
What allowed for the diversification of mammals?
the death of dinosaurs presented ecological opportunities for mammals, allowing for the exploitation of various open niches which lead to the mass speciation within mammals (aka adaptive radiation): rapid diversification accompanied with ecological diversification (in situ)
What was the goal in introducing Nile Perch in Lake Victoria?
introduced in the 1950s, the goal was to provide food for the residents
What happend when the population of Nile Perch exploded in regards to the cichlid population?
-the explosion of Nile Perch resulted in the mass extinction of over 200 cichlid species
What were the consequences of the extinction of the many cichlid species as a result of Nile Perch? (3)
-algae growth is unchecked (plant material left at the bottom of the ocean)-build up of not decomposed algae reduced O2 water levels causing other fish species to rise to the surface or go extinct-massive deforestation as nile perch must be dried over wood before consumption
What were the environmental changes that caused the Cambrian Explosion? (3)
-an increase of O2 concentration in the atmosphere-an increase in ozone thickness-calcium ions in the ocean rose
What were the ecosystem engineering developments that cause Cambrian Explosion?
animals had changed their environment opening up new niches (ex. burrowing)
What was found in terms of Hox genes that caused the Cambrian Explosion?
there was a strong correlation between # of Hox genes present in their lineage between the evolutionary order of animals appearing (morphological complexity and body size)
Mesozoic Era (2)
-era of reptiles-where mammals and angiosperms first appeared
Angiosperms
-flowering vascular plants with fruit and seeds
What do Angiosperms depend on animals for? (3)
-dispersal-defense-polination
Cenozoic Era
-its an us (mammal) era fr fr
Were angiosperm resources valuable?
Yes, primates had to compete against other species for angiosperm resources!
What are animals? (4)
-eukaryotic-multicellular-reproduce sexually-heterotrophic
How do transcription factors (like Hox) act compared to others?
on/off switches, whereas others set up gradients that trigger biological cascades
What happens if there are changes in Hox gene numbers?
morphological diversification; the animal is a quite different (increased complexity),ex. fish starfish jellyfish
What happens if there is broad changes in Hox expression?
morphological diversification; limbs and/or body change in size
What happens if there are subtle changes in Hox domain expression?
morphological diversification; limbs can be lost (ex. distaless (Hox) switched off in snakes causes no legs)
What happens if there is a change in regulation or function of downstream genes?
morphological diversification; ex. haltere in fly (little nub on the side) can grow into wings that aren't needed
What are some characteristics about the 6th Mass Extinction? (3)
-now!-global diversification on the decline for over 30000 years-extinction rate is 100-1000x greater than the background extinction rate
What is DNA barcoding?
classification of diversity based on a variable gene
What happens when pre-zygotic isolations do not exist
(pre zygotic isolation means no gene flow)-populations may interbreed to create hybrids which many erase distinctions between species (homogenization)
What are characteristics of primates? (4)
-opposable thumbs-nails instead of claws-BIG BRAINS-adaptations for many forms of locomotion
Anthropoids
both new world monkeys (NWM) and old world monkeys (OWM) + humans
Hominoids
apes + humans
Hominins
human lineage after the chimp + bonobo split
How do Hox genes work and what are they influenced by? (2)
-they encode proteins that bind to DNA to influence expression of other genes-they are influenced by promoters (ON/OFF) like distal-less gene in snakes -> no hind limbs
What causes increased complexity in a species?
the amount and changes in gene expression
What doesn't cause complexity in a species?
the number of genes
What did the primates of the Late Miocene/Early Pliocene era do?
they moved to a grassland habitat as a result of global cooling (decreased rainfall and seasonality shrunk tropical rainforest size and increased dry woodland and grassland habitats)
What are the reasons why hominins transitioned to bipedalism? (3)
-keep hominins cooler (less top SA and more side SA for wind)-frees up hands to forage and carry objects-increased dependence of offspring
Why didn't other species evolve bipedalism?
the theory is that suspensory locomotion (monkey swinging) pre-disposed the ape lineage to evolve bipedalism
What was the order of motion that lead to bipedalism?
suspensory motion -> knuckle walking -> bipedalism
What are ancestral features of Hominins 4-6 mya after the split from chimps + bonobos? (4)
-large canines-large brow ridge-small brain size-small molars
What are our derived features from the chimp + bonobo split of ancestral features? (4)
-forward location of the foramen magnum (signature of bipedalism)-small canine teeth-changes in femur and pelvis due to bipedalism-flattening of the face
Laetoli Footprints
earliest evidence of hominin bipedalism that looked at weight distribution of footprints
How are humans different from other apes? (4)
-fully bipedal-long young period-large BIG BRAINS-spoken language
What are some characteristics of Neanderthals? (5)
-faces that bulge in the middle-large brow ridge-larger brain capacity-more CHONKY (stocky)-shorter lower legs that are adapted for cooler areas
What were the findings of ordering the Neanderthal genomic sequence in relation to modern humans?
-all non-African MH shared 1-4% of their genome with Neanderthals-African MH shared close to nothing, suggesting gene flow occurred soon after MH left Africa
Who was more closely related to Neanderthals?
Denisovans were more closely related to Neanderthals than to humans
Was mixing common between Neanderthals and Denisovans?
Oui.
What are some characteristics about recent human evolution in relation to Denisovans and Neanderthals?
-each lineage had periodic gene flow with AMH-~7.4% of the Melanesian genome are derived from the Neanderthal + Denisova lineages-no other humans have denisovan DNA
What do Neanderthal genes in AMH do? (3)
-coping with UV radiation-increased risk of depression-tobacco use
What were the findings related to genotypic variations of human populations?
-93-95% of variation was shared among populations-the average proportion of genetic differences between individuals from different populations barely exceeds that between unrelated individuals from a single population (we are all super similar!)
Human Demography
the study of the characteristics of human populations such as size, growth, density, and distribution
What and when was the annual growth rate maximum?
around 1970 at 2.1% per year
What and when was the absolute annual increase in people?
around 1990 at 86 million people per year
Population Demographic Transitions related to old people
before 2000, the population of old people > the population of young people
Population Demographic Transitions related to people living in rural vs urban
before 2010, the population of rural living > the population in urban living
Population Demographic Transitions related to developing countries
before 1950, the ratio of population between less developed to developed was 2x, by 2050 this ratio will be increased to 6x
Is biodiversity evenly distributed?
Non.
Hotspots in relation to biodiversity (2)
-where a large chunk of biodiversity occurs-hotspots contain a large percentage of all diversity in plants and mammals comprising of now 1.4% (from ~12%) of the surface
Population in regards to biodiversity
-human density and growth rate is highest in biodiversity hotspots
Intrinsic Values of Biodiversity (3)
-all species rely on other species-genetic variation is necessary for adaptation-right to exist
Anthropogenic Values of Biodiversity
-direct value: goods (ex. food, medicine)-passive value (carbon and oxygen cycling, erosion and climate control)-information
Pros and Cons of Urbanization
Pros: good for economy and the use of marginally productive landCons: strains capacity
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