Evolution Part 1

polyphenism

a phenomenon when a single genotype can produce multiple distinct and stable phenotypes, often in response to environmental cues

locust

usually shy, solitary, and nocturnal but at high density they switch t a gregarious phase with bold, swarming diurnal and longer winged. initiated by mechanical stimulation of hind legs or combined sight/smell of locusts

phenotype plasticity

the ability of individual genotypes to produce different phenotypes in different environments

classical view

one gene, one trait Vp = VG + VE

constant traits

phenotypes with fixed expression across environments. Vp = Vg even across environments. the norm implicit across much of evolutionary biology

reaction norm

the distribution of phenotypes for one genotype over a range of environmental conditions. most traits are the product of an interaction between genes and the environment (G*E interaction).

measuring rxn norms

look at phenotype variation of the same trait across 2 or more environments, can use clones or lots of different genotypes as long as they are replicated across environments. slope = degree of plasticity. If slopes are not the sam there is a rxn norm. environment, sex and genotype matters.

mediating plasticity

mechs not always clear. strong signal of differential gene expression. genes with strong G * E interactions tend to have complicated promoter regions (at least in model organisms) some plasticity might rely more on developmental switches

plasticity commonality

important for sessile organisms like plants, still wide spread in animals

big 4 environmental factors

diet, temp (day length), predators/parasites and social environments. How organisms cope with environmental variations and how traits change over time.

reversible / irreversible

plasticity within an organism’s life time

adaptive vs nonadaptive

can affect wide range of traits → morphological, physiological, behavioral, and phenological (seasonal) changes, variation can be discrete or continuous

reversible plasticity

a response that can be induced and then lost. sometimes many times over an organisms lifetime induced defense can be costly

irreversible plasticity

environment affects trait early in development, no reversal after the fact

bluehead wrasse

individuals may begin life either as males or females but females can change sex later in life. induced by social environment. irreversible

adaptive plasticity

plasticity may be advantageous when it allows a genotype to have a broad tolerance to environmental conditions and thus have higher fitness

traditional perspective

genes lead and phenotype follow in the process of adaptive evolution. “genes as leaders”

alternative perspective

phenotype variation, even when it allows a genotype to have a broad tolerance to environmental conditions and thus have higher fitness.

canalization

evolution of internal mechs that constrain plasticity to consistently produces one phenotype

genetic assimilation

when a trait that initially appears only in response to environment becomes genetically “hard coded”. changes in threshold by which genes respond to the environment or loss of a threshold

plasticity and adaptation

new environment induces expression of novel and beneficial phenotype. expression of this phenotype then becomes genetically fixed through NS. can be further modified over time, plasticity pave the way for trait evolution and adaptation. environmental induction of novel traits due to plasticity could happen quickly and. be widespread across a pop. differential reproductive success could lead to loss of individuals without plastic response and eventually loss of plasticity via genetic assimilation

evolvability

the capacity of a system for adaptive evolution

bird migration

some species are facultative migrants meaning that they only migrate when climatic conditions demand it. migration is plastic response to the environment. some are obligate migrants and migrate every year no matter what

coevolution

reciprocal genes change in interacting species, owning to the NS imposed by each on the other

interaction types

species interact with many species at once. parasites, pathogen endosymbionts, prey, predators, direct and indirect effects. creates complex interactions web

mutualistic

effects are positive

antagonistic

effects are negative in one direction

commenalistic

no effects

geographic mosaic theory of coevolution

can find mutualism in some pops but antagonistic interactions between some species in other pops. selection can change across species and over time or space

hot spot

selection is strong in both species

cospeciation

speciation in one species leads to speciation in another

predators/prey

a relationship in which an animal ingests another. herbivores and plants → animals feed on plants. prey produces toxins to deter predators. predators evolve defenses against toxins. plants produce latex to prevent insects and insects stop latex production

deceptive pollination

a flower tricks an insect into visiting it without providing nectar exchange. releases pheromones and grows structures to look like females

host & parasite

virus, intestinal worm or other organism that lives in or on another and causes disease or death

brood parasitism

cuckoos don’t raise their own chicks → lay eggs in nests of other bird species. cuckoos evolve egg mimicry. parasite evolve better eyesight and parasitic identification

evolutionary arms race

coevolutionary isolation. species interact antagonistically in a way that results in each species developing adaptations against each other

character displacement

when a trait differs more btwn sympatric than allopatric pops of the same species

positive/positive mutualism

a relationship between species that raise each others fitness

pollination

insects and other animals visit flowers to gather nectar. plants benefit because the animals spread their pollen allowing them to reproduce.

seed dispersal

bird and mammals eat fleshy fruit. seeds egested. plants benefit from being dispersed across wide range

nutrient exchange

btwn plants and fungi. fungi in soil deliver minerals and other nutrients to plant roots, plants deliver organic C to fungi.

farming

some species of ants rear mushroom gardens in their nests. fungi grow and function as antibiotic to kill pathogenic fungi that invade garden

microbiota

humans and other animals depend on microbes to help digest food and synthesize vitamins

cleaners

some species of fish eat ecto parasites on the skin of the other fish.

symbiosis

long term interaction btwn two or more species

mutualistic coevolution

when each species benefits from the interaction

obligate mutualism

each party can only survive and reproduce successfully in the presence of the other.

faculatitive mutualism

mutualism is beneficial but not essential for the survival of each; interactions often vary over time and space.

commensalism

one benefits and the other is unaffected (or both unaffected)

rhizobia

bacteria that fix nitrogen becoming established in roots of legumes. require a host and provide plant ammonia.

Ants and Acacia

acacias repel herbivores with spores, pheromones and ants. queens lay eggs in hovels of trees. ants attack any predator of the plant. plants make nectar for ants

microbiomes

microbial community. community composition varies across body. has diverse health outcomes.

vertical transmission

directly from mother to embryo, some effects last longer than others. partially inherited microbiome

mimicry

form of convergent evolution in which it is advantageous for one species to resemble the other. shared signal received. 1. model → produce stimulus. 2. mimic → copy model, 3. predator → deceived by mimic

mullerian mimicry

multiple noxious species converge on the same warning phenotype.

batesian mimicry

one toxic species has a warning phenotype which is deceitfully imitated by harmless species

wallace’s three laws.

1 models and mimics must be found in the same geographic area

2 mimicry confined to a few groups (rare phenotype)

3 imitators must less abundant than model