module 1 + 4 good chris :) Flashcards
Natural Selection
is a process involving certain individuals who tend to survive and reproduce at higher rates than other members of a population due to their possessing certain inherited traits. Increases the correspondence between orgainsms and their environment
Evolutionary tree
groups of homologous characteristics to form a nested pattern, are more like hypotheses for which supporting evidence is still being collected
Evolution (genetics)
a change in a population allele frequencies over generations
Balancing Selection
preserves variation through many mechanisms, such as heterozygote advantage and frequency-dependent selection. Mat preserve variation at some loci, thus maintaining two or more forms in a population
Homologous structures are possesed by?
animals that probably evolved from the smae ancestor
stabilozing selection
favors intermediate variants in a population and culls extreme variants from the population. Acts against both extreme phenotypes and favor intermediate variants. Reduces variations and tends to maintain status quo for a phenotypic character
5 prezygotic barriers
habitat isolation temporal isolation behavioral isolation mechanical isolation gametic isolation
Postzygotic barriers
reduced hybrid viability, reduced hybrid fertility, and hybrid breakdown
Clear speciation has occurred when?
A gene pool changes establish reproductive barriers between two populations
What prevents speciation from occuring?
viable fertile hybrids
Hybrid zones
Region which members of different species meet and mate, producing at least some offspring of mixed ancestry
Morphological species concept
distinguishes between species body shape and other structural features
Genetic polymorphism
the occurrence in the same population of multiple discrete alletic states of which at least two have high frequency
The Hardy-Weingberg equation
determines what the genetic makeup of a population would be if it was not evolving at the locus. In a population that is not evolving allele and genotype frequencies will remain constant from generation to generation
5 conditions for Hardy Weinberg Equilibrium
- No mutation
- Random mating
- No natural selection
- Extremely large population size
- No gene flow
Antibiotics
any compound used to control bacteria infections
Promiscuity of bacteria
their ability to exchange genetic information with other bacteria (either same or different species) very rapidly. They pick up genes for resistance easily
Mild Selection
a condition that isn’t so drastically different that the bacteria must evolve antibiotic resistance immediately. They have a “ramp” where they have time to adapt to the environment and develop resistance
Founder effect
A major shift in distribution. Reduced genetic variability is newly formed populations at the vanguard of a moving species distribution may be incapable of adapting to the changing environment, if they have low genetic variation
Bottle necks
Random changes in population size due to a reduction from a natural catastrophe, annihilated population, elimination of most, and leave small group behind (random selection)
- population regrows
gene flow
the movement of alleles from one population to another, as would happen when individuals from different populations interbreed
Genetic Drift
chance events also cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations
4 effects of genetic drift
- is significant in small populations
- genetic drift can cause allele frequencies to change at random
- Genetic drift can lead to a loss of genetic varaition within populations
- can cause harmful alleles to become fixed
Directional Selection
occurs when conditions favour an individual one extreme of a phenotypic range thereby shifting a populations frequency curve for the phenotypic character in one direction or the other
Frequency dependent selection (4 factors)
The fitness of a phenotype depends on how common it is in the population
- selection can act only on existing variations
- evolution is limited by historical constraints
- Adaptations are often compromises
- Chance, natural selection and the enviroment interact
Speciation
the process by which one species splits into two or more species
Reproductive Isolation
the existence of biological factors (barriers) that impede members of two species from interbreeding and producing viable fertile offspring
4 Evolutionary forces and their role in divergence
- Mutation: is likely to occur independently in the separated populations
- Genetic drift will always tend to force divergence of separated populations
- Gene flow will genetically homogenize populations making them similar to one another
- Natural selection is the wild card
Allopatric speciation
(different land): populations are separated by physical barriers
Sympatric Speciation
(same land): happens without an obvious barrier. Without physical separation, there is the potential for gene flow to homogenize diverging populations
genetic exchange that occurs in hybrid zones (3 outcomes)
- hybrid zone is stable du to hybrids are only viable in the specific habitat
- is genetic homogenization between the 2 species that are hybridizing
- Reinforcement occurs when hybrid progeny suffer poor viability or dramatically reduced reproduction. Production of hybrids is strongly selected against when two species come into contact
Morphological species concept
characterizes a species by body shape or other structural features and suggests that each species is morphologically distinct
Ecological species concept:
views a species in terms of it ecological niche, the sum of how members of the species interact with the nonliving and living parts of their environment
Phylogenetic species concept:
defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life
Polyploidy
Species may originate from an accident during cell division that results in an extra set of chromosomes
Autoployploid
Is an individual that has more than two chromosome sets that are all derived from a single species
3 phases of speciation
- Separation of species or a cohesive gene pool into one or more groups isolated from gene flow
- Genetic divergence of these groups
- The separated gene pools become reproductively isolated from one another
Adaptive radiations
periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles, or niches in their communities
Phylogeny
hypothesis for the evolutionary history of a species or group
- represented in evolutionary trees
Basal taxon
A lineage that diverges early in the history of a group
monophyletic
ancestral species and all of its descendants
Paraphyletic
ancestral species and some not all descendants
Polyphyletic
include distantly related species but not their most recent common ancestor
orthologous genes
found in different species and their divergence traces back to speciation events that produced the species
Paralogous genes
the homology results from gene duplication, hence multiple copies of these genes have diverged from one another within a species
- they have different function in different species, but look the same
Horizontal gene transfer
process in which genes are transferred from one genome to another through mechanisms such as the exchange of transposable elements and plasmids. Viral infections and fusions of organisms. Is known to occur within both prokaryotes and eukaryotes
What does a branch point on evolutionary tree represent
the common ancestor of the lineages following in evolutionary time
Vesitigial structures
homologies that appear to have marginal, or no importance to an organism
Two major problems that were solved for plants, animals and fungi to becom terrestrial
reproduction and prevention of dehydration
What was the likely firsy source of oxygen for the oxygen atmosphere
Cyanobacteria
Maximum parsimony
principle that allows systematists to narrow the possibilities when they are constructing a phylogenetic tree for a large number of species
Outgroup
a species or group from an evolutionary lineage that is known to have diverged before the lineage that includes all the species under study
Simple behaviours
fixed action patterns (simple relatively unchangeable behavior that usually goes to completion once it has been elicited) is elicited by a relatively simple sign stimulus
Sequential steps of communication signals in courtship
(I) males orients via visual and olfactory (cuticular hydrocarbons) communication with the females
(II) males then use tactile communication- tapping the female which elects more chemical release by the female
(III) the male then signs to the female by vibrating his wings (auditory communication)
4 types of social behaviour
- cooperation: both benefits is strongly favoured by natural selection
- Selfish: actor (the individual that initiates the behaviour) benefits (increase in its fitness relative to the recipient, natural selection also favoured)
- Altruistic: the fitness of the actor decreases which causes the fitness of the recipient to increase
- Spite: both are harmed, causing evolution to be very difficult
Inclusive fitness
The total fitness of an individual is related to the individual fitness as well as the fitness of relatives
Kin selection
natural selection in favour of behaviour by individuals that may decrease their chance of survival but increase that of their kin
Eutrophic
a lake that is nutrient-rich and oxygen-poor
- salinity, oxygen, and nutrient concentrations differ among lakes and seasons
- Eutrophic lakes are depleted with oxygen in the deepest zone
- the amount of decomposable organic matter in bottom sediments is high in eutrophic lakes
- high rates of decomposition causes the periodic oxygen depletion
Oceanic pelagic zone
a region that is vast of open, blue water
- constantly mixed by wind-driven oceanic currents
Eustary
a region that transitions between the river and the sea
- seawater flows up the estuary channel during a rising tide and flows back down the channel during a falling tide
- high-density seawater occupies the bottom of the channel and mixes with the lower-density river water at the surface
How is carrying capacity determined by?
In a population it is determined by the limiting resource
K selection
life-history traits that are favoured at high population densities
Mullerian mimicry
two or more unpalatable species resemble each other, causes predators to quickly learn to avoid such prey they encounter
Commensalism
Interaction between species that benefits one of the species but neither harms nor helps the other species
Greatest cause of extinction
habitat alteration
Consequence of rising CO2 levels?
Increased vegetative productivity
The break down of the ozone layer in the stratosphere
result of the formation of chlorine monoxide (CIO) and oxygen (O2)
destruction of the ozone layer is linked to the release of chlorofluorocarbons (CFCs) into the atmosphere
Possible reasons for pheromone release
- to signal danger
- to attract males during courtship
- to inhibit the development of sex organs
- to transmit species-specific information
Coefficient of relatedness
the fraction of genes that, on average are shared by two individuals
Extinction affects what group the most?
Affects top predators
- restructuring after an extinction leads to a new top-down control of food chains
- new weapons and new defences
convergent evolution
The acquisition of the same biological trait in different lineages
- not from common ancestor
What is the best definition of evolution
a) change in phenotypic makeup of a population
b) change in genetic makeup of a population
c) change in genotypic makeup of an individual
d) change in the environmental conditions
b)
Simplest to most complex level of biological organization
- cell
- tissue
- organ
- individual
- community
- population
Beneficial mutations (e.coli)
12 populations and in each a random beneficial mutation occurred.
- fitness increased in the first 20 000 generations
- E.Coli tried out every mutation possible
- number of the lines (populations) became mutators and have elevated the rates of spontaneous mutation
Heterozygote Advantage
some heterozygous loci are more adaptive because they confer organisms with better fitness or they protect the organism from harmful effects of the allele in homozygotic state
Sickle Cell amenia
shape of cells
-homozygotes with the normal red blood cell allele have normal RBCs
- heterozygotes for sickle cell amenia have a mixture of both cells
- homozygotes for the allele (sickle cell amenia) have misshapen RBCs and tend to clog the vessels
Sickle cell amenia allele: individuals suffer and die before reproductive maturity (zero fitness)
Why do females choose extravagently ornamated males?
The ornaments are indicative of high genetic quality, either they are costly to produce or leave a male vulnerable
- resilient male has survived to strut on the breeding ground
p^2 + 2pq + q^2 = 1
P^2- frequency of the homozygous dominant genotype
pq- heterozygous genotype
q^2- frequency of homozygous recessive genotype
Populations on oceanic islands are genetically different from continential populations of the same species this is due to
I) island individuals mate at randon where as continental individuals mate non-random
II) genetic differences arise due to founder events during island colonization
III) little gene flow between island and continental populations
iv) island populations become adapted to local environments
II, III, and IV
Convergent evolution is the result of..
adaption to similar selection pressures
What is the goal of natural selection
Adaption to the environment
Grey tree Frogs (mate choice)
- female grey tree frogs prefer males that have longer more complex calls
- good genes to be healthy = longer calls
Semelparous species
individuals will reproduce once and die
Iteroparus species
individuals have multiple reproductive bouts. “itero” means repeated and “parous” refers to production
Competition
occurs when both species are supressed in terms of their population growth by their interaction with other species (negative negative interaction)
Exploitation
one species benefits at the expense of another
mutalism
both species benefit from the interaction and there seems to be no consequences for the other
Amensalism
one species suffers but the other one receives no benefit
Evolutionary consequences
one species becomes a selective pressure, causing an evolution in the other species. Interactions are not static, dynamic across generations as both species involved experience evolutionary change feedback
Two types of competition
Interference: involves direct antagonistic behavioral interactions between competing species
Exploitative: species negatively effect each other through the use of a shared, limiting resource and may never interact
Commensalism
interactions that benefit one species and have a neutral or beneficial effect on the other
- experience some effect be that slightly positive or negative which tips it to slightly mutualistic or exploitive
Species diversity vs richness
Richness: the number of species that occur in an area
Diversity: is a function of both species richness and species evenness
trophic structure
primary producers: capture sun energy and stores energy in complex biomolecules
Primary consumers: directly consume primary producers,
Secondary eat those herbivores (and it layers after)
Keystone Species
not abundant but very important
Top down vs bottom up control
• The structure of a community is primarily influenced by the lowest trophic level (photosynthetic producers)
○ Food supply from lower trophic levels limits the species diversity and interaction at higher trophic levels
Bottom-up control (food availability hypothesis)
Top-down: regulated by apex predators (predation hypothesis)
Intermediate disturbance hypothesis:
when habitats are left undisturbed that are colonized by very competitive species that exclude many other species (competition reduces diversity)
Primary succession
that starting habitat is virtually lifeless and the soil is more or less mineral and has no biological content. Takes a long time and depends on the sequence with which species arrive in the habitat (some early arriving species may facilitate colonization by later species through their effect on soil development)
Secondary succession:
when an existing community has been disturbed but the soil has been left intact( forest fires). Succession occurs quickly and the habitat often returns to its original state
GPP (gross primary production)
the amount of energy from sunlight converted to chemical energy of organic molecules per unit time by autotrophic organisms
NEP(net ecosystem production
is the gross primary productivity minus the respiration of all living things in the ecosystem
- indicates whether an ecosystem is gaining or losing carbon over time, important if trying to figure out the global carbon budget and implication for global warming
Detritus
once living organic matter, is removed from the photic zone as it settles into deeper water
detritivores play a critical role in recycling chemical elements back to primary producers.
Net secondary production
energy stored in biomass that was produced by growth and reproduction of herbivores eating primary producers
• Only energy capture in herbivore consumers will be available to secondary consumers
Production efficiency
the net secondary production divided by the assimilation or eating of primary production (percent)
Move up the food chain production efficiencies will lower
Tropic efficency:
percentage of production transferred from one trophic level to the next, generally low, only about 10% and range 5-20% depending upon the type of ecosystem and particular species in the food chain
Carbon cycle
IS gaseous in both CO2 and methane
• Carbon enters living things through photosynthesis and is subsequently transmitted up food chains. As you can see, there’s a lot more carbon stored in dead things than in living things, and the release of C02 through decomposition is strongly dependent on temperature.
• Carbon is also released by methanogenesis release CH4 and CO2 during anaerobic decomposition (methane 35 times more potent than CO2)
Phosphorous cycle
- Cycling phosphorus is simple as it does not have a gas phase
- However phosphate can be lost from ecosystems when it is leached from the soil and precipitates out in water, sinking to the bottom of aquatic habitats, especially oceans and then laid down into new sedimentary rock
- Phosphate discharged in agricultural and domestic sewage often cause cultural eutrophication of aquatic systems
consequences of phosphorous cycle and humans
- One inorganic form (PO4), Weathering of rocks
- Local cycling via decomp
- Precipitates in water, Cultural eutrophication
