Biological Evolution Flashcards
define biological evolution
DESCENT WITH MODIFICATION through the mechanism of NATURAL SELECTION
define microevolution
small-scale evolutionary change within the species level, caused by changes in allele or genotype frequencies that occur within a population of a particular species over a few generations
define macroevolution
large-scale evolutionary events over geological times, resulting in phenotypic changes in populations that create at least a new species
involves descent of different species from shared ancestors over many generations
state the two essential features of Lamarck’s theory of evolution
use and disuse of organs
inheritance of acquired characters
what does “use and disuse of organs” mean?
when an organism developed a need for a particular structure, its development was induced
what does “inheritance of acquired characters” mean?
beneficial characteristics could be inherited
(false)
state the seven essential features of darwin-wallace’s theory
- organisms have great potential to reproduce
- environmental restrictions / constancy in numbers
- struggle for existence / survival
- variation within a population
- survival of the fittest by Natural Selection
- differential reproduction (like produces like)
- formation of new species
define natural selection
process by which the environment selects for fit individuals with inherited traits that are best suited to the local environment. individuals with selective advantage are more likely to survive and reproduce, producing more offspring
define natural selection
process by which the environment selects for fit individuals with inherited traits that are best suited to the local environment. individuals with selective advantage are more likely to survive and reproduce, producing more offspring
what are the two essential features of darwin-wallace’s that explain the tendency to reproduce more than can survive?
organisms have great potential to reproduce + constancy in numbers / environmental restrictions
what is fitness in evolution?
relative reproductive success of individuals within a population in leaving offspring in the next generation
OR
relative success of a genotype compared to others
define adaptation
an evolutionary modification that improves the chances of survival and reproductive success in a given environment
what is the main difference between darwinism and neo-darwinism?
neo-darwinism includes principles of Mendelian genetics and knowledge of molecular biology (eg. mutations and allele frequency changes)
what are the different essential features of neo-darwinism compared to darwinism?
- variation within a population
- survival of the fittest by Natural selection
- differential reproduction (like produces like)
- formation of new species
what does neo-darwinism include about variation within a population that darwinism did not?
variations are a result of spontaneous mutations, not due to individual needs
variation is controlled by genes
what does neo-darwinism include about natural selection that darwinism did not?
individuals with genetic variations best adapted to the environment have a selective advantage
what does neo-darwinism include about differential reproduction that darwinism did not?
proportion of fit individuals with favourable genes and a selective advantage increases with each generation
what does neo-darwinism include about formation of a new species that darwinism did not?
speciation is due to natural selection AND separation of population (no interbreeding)
define anatomical homology / homologous structures
structural / anatomical similarities in homologous structures, which suggest they descended from a common ancestor with that feature
similarity in characteristics resulting from a shared ancestry
give examples of anatomical homology
forelimb and hindlimb bones of vertebrates
forelimb descended from pentadactyl limb (5 fingers)– human arm, cat limb, whale flipper, bat wing
vestigial structures
early embryonic development: chicken and humans have pharyngeal pouches and post-anal tails
define divergent evolution
a common ancestor subject to different environments and selection pressures diversified into different species
what is genetic isolation?
genetically compatible interbreeding natural populations that is genetically isolated from other such groups
how is the genetic species concept applied, and what are its limitations?
mitochondrial and nuclear genomes
common gene pool and karyotypes may change due to: directional selection and interbreeding btw 2 specieis
define the biological species concept
know this!
a species is a population whose members can interbreed in nature to produce Viable, Fertile Offspring (VFOs)
what is reproductive isolation?
the existence of biological factors that prevent members of different species from producing VFOs
barriers are known as Reproductive Isolating Mechanisms (RIMs)
state the two types of RIMs that may be found in reproductive isolation
prezygotic barriers: impede mating or hinder fertilisation
postzygotic barriers: fertilised zygote cannot form VFOs
what are the four types of prezygotic barriers / RIMs that prevent mating?
- habitat (including geographic)
- temporal: different maturing times
- behavioral
what are the two types of physiological isolation (prezygotic RIMs, after attempted mating)?
mechanical: size, incompatible genetalia
gametic: gametes cannot fuse
what are the two types of postzygotic barriers / RIMs (after fertilisation)?
physiological isolation
- hybrid inviability: zygote does not develop (not viable)
- hybrid sterility: zygote survives, but cannot mate (not fertile)
what are the advantages of the biological species concept?
(it’s the VFO one) focus on reproductive isolation, which is how speciation occurs
what are the limitations of biological species concept?
cannot be used on:
- fossils
- asexually reproducing organisms (eg. prokaryotes, hermaphrodites)
many groups have gene flow, but are still species (biological separates species by lack of gene flow)
what is the phylogenetic specieis concept?
species: smallest group of individuals that share a common ancestor
what are the advantages and limitations of the phylogenetic species concept?
advantages: can reveal “sibling species” that cannot morphologically be distinguished
limitation: determining the degree of difference required to indicate separate species
what is the morphological species concept?
distinguishes species by body shape and other structural features and similar anatomical traits
what are the advantages of morphological species concept?
can be applied to all sexual / asexual organisms
useful even without gene flow info
what are the limitations of the morphological species concept?
- difficult to analyse continuous quantitative traits
- degree of difference needed to distinguish species unclear
- morphology is not accurate (some same species look v diff, diff species look v same)
what is the ecological species concept?
ecological niche within native environment of species
unique adaptations to particular roles in a biological community
what are the advantages and disadvantages of ecological species concept?
advantages: for sexual / asexual organisms (useful for bacteria)
limitations: does not consider morphology and reproductive compatability
define speciation
evolution / origin of species
state the four stages of speciation
- single population
- barrier develops (geographical / ecological isolation)
- differentiation due to diff selection pressures
- RIMs, reproductive isolation (even if geog / ecological barrier disappears)
during the second and third stages of speciation (geographical / ecological isolation), can the subgroups interbreed?
2nd: yes, speciation has not occured and they are still the same species, just separated
3rd: no, RIMs are developing and gene flow is interrupted
state the two main modes of speciation
allopatric: geographical isolation
sympatric: ecological isolation or polyploid organisms
what is allopatric speciation?
formation of new species when one group is geographically separated from the rest of the species, evolves by natural selection and / or genetic drift
(no gene flow btw subgroup and original pop)
what is sympatric speciation?
new species evolves within the same geographic region as the parental species OR geographically overlapping populations
what type of sympatric speciation is immediate speciation, and how does it occur?
polyploidy: organisms possess more than two of haploid chromosome set
non-disjunction during anaphase I or II, when homologous chromosomes or sister chromatids respectively fail to separate
what are the two types of polyploidy in sympatric speciation?
autopolyploid: more than 2 sets of chromosomes from a single species
allopolyploid: more than 2 sets of chromosomes from two or more species
(normally sterile, chromosomes are non-homologous and cannot pair during meiosis)
what are the two models that explain the rate of evolutionary change?
punctuated equilibrium
phyletic gradualism
what is biological classification?
act of systematically arranging organisms into groups based on particular shared characteristics (mainly morphology) and similarities
state the hirearchy of biological classification
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
DKPCOFGS: do keep pond clean or frog gets sick
what is adaptive radiation?
evolutionary diversification of many related species from one or a few ancestral species in a relatively short period of time
what are the two reasons adaptive radiations occur?
- ecological opportunities
- availability of new or novel types of resources not exploited by ancestral organism
- colonising species has no competitors, succeeding generations diversify - evolutionary novelties
- modification of pre-existing structures: morphological innovation
define extinction
end of a lineage, occurs when the last individual of a species dies
permanent loss: once a species goes extinct, it never reappears
eventual fate of all species, encourages adaptive radiation
what are the two rates of extinctions?
- uniform / background: continuous, low-level
- mass extinction:
- causes: climate change, catastrophies, interspecies competition (humans)
- followed by adaptive radiation
define biodiversity
variety of living organisms (species) and their range of behavioral, ecological, physiological and other adaptations in an area such as an ecosystem
what is systematics in biodiversity?
scientific study of biodiversity, classifying organisms and determining their evolutionary relationships / history
what is phylogeny?
evolutionary history, branching relationships of organisms as they give rise to multiple descendent species over evolutionary time
what are monophyletic, polyphyletic, paraphyletic taxons?
monophyletic: ancestral species and all its descendents
polyphyletic: several lines with no recent common ancestor
paraphyletic: common ancestor and some but not all descendents
what is a clade in a phylogeny tree?
monophyletic group: all descendants of a group’s most common ancestor and no other members
compare homology and analogy in evolution
homology: divergent evolution
analogy: convergent evolution
what are plesimorphies?
shared ancestral characters from a common ancestor that remain present in all groups of descendants (eg. backbone)
what is the relationship between the degree of homology / similarity in primary sequences of macromolecules and relation of species?
greater degree of homology = more closely related
what are the nine advantages of molecular methods in the study of evolutionary relationships?
- genetically passed down
- can be used on all organisms
- huge database
- shows relationships not shown by non-molecular methods like homology
- quantifiable
- provides info ab evolutionary process
- more organisms getting sequenced, can be compared w more species
- reconstruct phylogenies, and other microorganisms with no fossil record
- diff genes evolve at diff times even in same evolutionary lineage (can see short or long times depends on gene used)
what are molecular / biochemical homologies?
nucleotides in DNA / RNA and amino acids in proteins: share genetic code
- as descendents evolve independently, they accumulate more and more differences in their DNA
what are the roles of fossil records in deducing evolution?
- indicates time of origin and extinction of species (based on which rock layer their fossils are found in)
- shows evolutionary changes that have occured over time in groups of organisms
compare the anatomy of ancestral horses (hyracotherium) and modern-day horses (equus)
- small –> big
- 4 toes in front, 3 toes in hind –> one toe each
- small and simple teeth –> larger and more complex teeth
how does the fossil record support darwinism?
discovery of transitional fossils link older organisms to modern species
- support idea that diversity of life arose from common / shared ancestry
define biogeography
the study of the range and geographical distribution of extinct and modern species of organisms in different places throughout the world
what is the role of islands in evolution? (common qn)
islands generally have many species that are endemic (unique to the island)
- descended w modification from a mainland ancestor
define convergent evolution and analogy
species from different evolutionary branches resemble each other if they have similar ecological roles and faced similar natural selection pressures
- analogy: convergent evolution of the same trait
define population genetics
study of genetic composition and variability of a population
- frequency and distribution of alleles
- genotypes
define a population
group of same species that live in a defined geographic area
- capable of interbreeding to produce VFOs (biological species concept)
- smallest unit that can evolve
define gene pool
total collection of all genes of all breeding individuals (represented by their gametes) in a population
define allele / genotype frequency
relative proportion of alleles / genotype present in a population
what are the five causes of genetic evolution (fingers on hand)?
thumb: natural selection (favours good traits)
index: movement leads to gene flow
middle: mutation
ring: non-random mating
pinky: small population
what is the hardy-weinberg equilibrium / principle?
frequencies of alleles and genotypes in a population’s gene pool remain constant across generations (if there are no sources of genetic variation: five fingers)
define microevolution (impt!)
changes in allele / genotype frequencies that occur in a gene pool over time
define natural selection
process by which certain individuals that are better adapted to an environment survive to reproduce (differential survival and reproduction), increasing the frequency of favourable genotypes / alleles in gene pool, adapting the resultant generations to its particular environment
state the three types of natural selection
- directional
- disruptive
3, stabilising
describe directional natural selection
- one extreme phenotype favoured
- population mean shifted for selected character
eg. peppered moths
describe stabilising natural selection
- existing mean / intermediate phenotypes favoured
- extremes selected against
- reduction in variance
eg. heterozygosity for sickle-cell in malaria-prone areas
describe disruptive / destabilising natural selection
- favours both extreme phenotypes
- mean / intermediate selected against
- may form new species!
eg. black bellied seedcrackers (either big or small beaks for diff seed types)
define genetic drift
random change of allele and genotype frequencies as a result of chance alone
differs from generation to generation in a small gene pool
what are the four effects of genetic drift?
- significant in small populations
- random change of allele frequency
- loss of genetic variation within populations, causes genetic divergence within populations
- may fix harmful alleles
how does the founder effect cause genetic drift?
one or few individuals colonise an isolated habitat
eg. human amish population, inbreeding: ellis-van creveld
how does the bottleneck effect cause genetic drift?
large-scale catastrophic events causes drastic short-term reductions of population size
- survivors represent small random population
- alleles may be under-represented, over-represented, eliminated
- reduction and restriction in genetic variability
eg. great prairie chickens in US
define gene flow
movement of genes / alleles from one population to another (by migration), so the gene pool gains or loses alleles
what is the heterozygote advantage?
heterozygous individuals for a particular gene have greater fitness than homozygotes
eg. sickle cell anemia in malaria-prone areas
what is frequency-dependent selection?
balancing selection, maintains two different phenotypic forms in a population
- scale-eating fish in Lake Tanganyika, left and right jawed
give the rough structure of natural selection qns
DNA mutation = selection pressure of = selective advantage (selected for) = survive and reproduce = pass on gene = increase in alleic frequency
