unit 6 - evolution Flashcards
evolution definition
the change in heritable characteristics of a population overtime (change in frequency of alleles in gene pool)
what are acquired characteristics + ex
change in characteristics of organisms during their lifetime ex. trees can grow asymmetric if exposed to strong winds
what does lamarckism believe
belief that characteristics acquired during lifetime can be passed down to offspring and states that structures used frequently will strengthen and one unused will deteriorate
issues with lamarckism
- acquired traits are not heritable
- environment doesn’t change base sequence of genes <- need changes in germline for inheritable traits
pragmatic truth definition
a truth that works
truth = everyone agrees on reality
- observations form generalizations which are tested -> if supported, theory emerges -> theory can explain/predict future observations, it’s a pragmatic truth
how are genes and protein sequences evidence for evolution
- when heritable characteristics change, DNA/protein sequences change
- if base sequences of same gene in diff species have few diffs -> closely related and vice versa
- can be represented with cladograms
how is evidence for evolution present in fossil records
- rock layers at top = recent
- sequence in which fossils are found in rock match sequence in which they’re expected to evolve
- discovered sequences fit ecology of organisms (plants b4 animals, plants suitable for pollination before pollinators)
- fossils have been found showing transition of ancient species to present day descendants
fossil record meaning
sum of all discovered and undiscovered fossils and their relative placement in rock
why are there gaps in the fossil records?
- unideal conditions for fossilization
- only hard parts of organisms preserved
- damage of fossils = only fragments left
transitional fossils definition
fossils that have traits similar to both ancestral species and descendant species
how is evidence in evolution present in selective breeding (ex. corn)
- yellow corn didn’t exist in nature, its a result of artificial selection of a wild grass called teosinte
- random mutations occur and farmers select ones with desirable traits
- farmers planted seeds of corn with largest kernels so offspring would have same characteristics-> became most common type
- new corn produces fewer ears, softer + larger kernels
how does selective breeding provide support of natural selection
- through artificial selection, drastic changes occur over short periods of time providing support for possible changes that may have occurs over billions of years due to natural selection
how is evidence of evolution present in homologous structures?
ex. pentadactyl limb
- inherited from common ancestor, but evolved differently to adapt to unique needs of organism
what are homologous structures?
same anatomical structures but diff functions on diff organisms
what are analogous structures?
characteristics that look similar but have different underlying anatomical structures
how is convergent evolution present through analogous structures?
diff anatomical structures became similar due to similar needed function to adapt to similar environment
central nervous system as an analogous structure
- large number of organisms with bilateral symmetry <- suggests common ancestry
- annelids, anthropods, vertebrates have single nerve cord running down midline
analogous structures: human eye vs. octopus eye
- similar but have significant structural differences
- human: nerve fibres in front of retina = blindspot
- octopus: nerve fibres behind retina = no blindspot
- shows different origins that converged to similar function
what must occur for natural selection
- reproduction of more organisms that can be supported by environment
- variation in characteristics
- variation in fitness
- heredity of characteristics
why does overproduction of offspring promote natural selection
- increased competition for resources<- not every organism will survive
- density dependent abiotic factor
variation in asexual organisms
- relies on mutations
- in times of change, may not mutate fast enough for populations to survive
what can variation be the result of?
- random mutations (DNA replication, viral infections)
- sexual reproduction (meiosis, random fertilization)
adaptations definition
structures/characteristics that make an individual suited for environment/way of life <- don’t develop in individuals lifetime
selection pressure meaning
any reason for organisms with certain phenotypes to have survival advantage/disadvantage
fitness meaning
how well adapted an individual is to their environment (how well they can survive and reproduce successfully)
how does natural selection work
- traits giving advantage are selected for
- organisms with trait are better suited to survive and reproduce
- if more organisms with the trait survive compared to w/o the trait, more offspring will have the trait
gene pool definition
all genes and their different alleles present in population
how is sexual selection a selection pressure +ex
- sex for females is more “costly” so they choose mate who is “best adapted” to environment
- ex. male deers w antler shows they are healthy, have enough nutrients to grow such structures
why do females prefer exaggerated traits in males?
ex. courtship dances -> male has extra energy to spare, he’s strong and well fed
ex. elaborate feathers -> male’s ability to survive predators even while standing out
conclusion of john endler and guppy experiment
- investigated effect of predation on physical traits of guppies
- colouration: more attractive to females but more visible to predator
- therefore, fewer predators = more colourful guppies, more predators = less colourful guppies
results of antibiotic resistance
- since antibiotic discovery, more bacteria have become resistant
- more resistance = more antibiotics needed
- when antibiotic has multiple resistances, can lead to widespread strains
how does antibiotic resistance develop
- bacteria reproduces, random mutation into resistant strain
- when antibiotic used, non resistant strains die, only resistant strain lives
- resistant strain reproduces, weaker ones die, leaving only the very resistant strain
- continues to reproduce
what causes antibiotic resistance in bacteria to evolve so quickly
- widespread use of antibiotics
- misuse of antibiotics
- bacteria can reproduce very quickly
- bacteria populations are big = mutations of resistance more likely
- bacteria can share DNA
what is directional selection + graph
- most of evolved population have same change in characteristics
ex. pop. of mainly grey rats evolve to become mainly black rats - evolved pop. parabola shifted right or left of original
what is diversifying selection + graph
- evolved population splits into two extremes
ex. pop of mainly grey rats evolve so half are white and half are black - m shaped parabola
what is stabilizing selection + graph
- evolved population has more of the same traits
ex. pop of mainly grey rats evolve into all grey rats - parabola becomes steeper than original
species definition
group of organisms that can successfully interbreed and produce viable offspring with each other but not other groups
what are the steps to speciation
- if population separates -> likely will experience diff ecological conditions
- over many gens, characteristics of the two new populations will diverge as result of nat. selection in unique environments
- if two pops meet again, may not be able to mate
- gene flow b/w pops is reduced -> species separate into 2 unique species
speciation definition
the formation of new and distinct species in the course of evolution
what causes speciation occur
geographical isolation, behavioural isolation, temporal (time) isolation
example of geographical isolation that leads to speciation
- aka allopatric speciation
- some individuals may migrate to island, or road may separate habitat
example of behavioural isolation that leads to speciation
- fish feeding near shore vs. deeper water, birds preferring different mating songs
example of temporal isolation that leads to speciation
- a type of sympatric speciation = occurs in same geographical area
- ex. plants flower in different seasons
when does speciation often occur
- a population extends its range through migration to an island
-explains large # of endemic species on islands
endemic species definition
species only found in certain geographical areas
adaptive radiation meaning
a rapid increase in the number of species with a common ancestor, characterized by great ecological diversity
speciation of bonobos and chimpanzees
- geographically isolated by congo river that used to be shallow, chimpanzees could cross it
- at some point, river rose, isolating chimps on both sides
- founder pop faced diff selective pressures and evolved into bonobos
founder population meaning
when a small group of the population breaks away and starts a new population
why are hybrids naturally prevented
- often hybrids are sterile, so resources spent on creating them are wasted as they cannot pass alleles down
- preventative measures are categorized into prezygotic isolation and postzygotic isolation
what is prezygotic isolation + examples
- to prevent a zygote from being made
- ex. diff mating songs/dances, physical compatibility, species don’t interact
what is postzygotic isolation + examples
- to prevent zygote from development
- ex. hybrid inviability (zygote may die during development), hybrid sterility (offspring is sterile)
what is an apex predator
a predator at the top of the foodchain
