evolution - 05.07

how did charles darwin define evolution

"descent with modification," the idea that populations can change over time when individuals differ in traits responsible for survival + reproduction (survival of the fittest)

what do we use to find evidence of evolution

biogeography
comparative morphology
geological discoveries
radiometric dating
stratigraphy
molecular clocks

biogeography

discovery of new organisms in new places + discovery that organisms living in different parts of the world have different traits

for example, one group of spiders in venezula could have different traits than another group of spiders living in russia
also, think race evolution: how ppl living in different parts of the world evolved differently (hooked noses for middle easterns b/c of deserts, wider noses for africans b/c of hotter climates)

comparative morphology

study of body plans and structures among groups of organisms

animals that are very different from one another could share structures, like whales and bats sharing similar forlobes

some parts have no function, like the human appendix

when it comes to introducing change in morphology, evolution tends to follow the path of least resistance (easy, long-term)

geological discoveries

can predict the relative age of fossils found in strata

older = deeper + simpler
younger = shallow + more detailed structure

some fossils of extinct animals are related to known species, like types of dinosaurs and birds

fossil record

the millions of fossils that scientists have collected + their relative age

can look at patterns in the fossil record to understand the history of life

for example, there has been an increase in structure complexity over time, which scientists can tell by looking at the structures between older and newer fossils

radiometric dating

relies on radioactive elements to date fossils

stratigraphy

uses the geological timeline to predict the order and placement of fossils on it

molecular clock

uses the mutation rate of biomolecules to deduce the time in prehistory when life forms diverged

what is needed for evolution to occur

variation
inheritance
selection
time

variation

differences in physical traits of an individual from the group to which it belongs

all life forms in a group vary slightly

inheritance

genetic material is passed from parents to their offspring

selection

organisms with traits that are more favorable to their survival and reproduction are more likely to pass their genes down to the next generation, until every organism in the population has it

why is time needed for evolution

major changes often take many thousands of generations, meaning decades if not centuries of time to completely evolve

gene pool

all of the genes in a population

variation in phenotypes

because each gene in a gene pool can have many alleles, and individuals inherit these different allele combos, there's variation in their phenotype

genetic equilibrium

situation in which allele frequencies remain constant, aka population is not evolving

what determines alleles in an individual/how do alleles meet?

- crossing over at meiosis 1
- independent assortment
- random alignment
- fertilization

what are the five conditions required for genetic equilibrium

- no mutation
- random mating
- gene doesn't affect survival/reproduction
- large population
- no immigration/emigration

does genetic equilibrium every actually happen?

rarely in nature

microevolution

a change in allele frequency within a population

drives a population away from genetic equilibrium

how is microevolution brought about?

mutation
migration/gene flow
genetic drift
natural selection

gene flow

purposeful movement of alleles from one population to another

genetic drift

random change in allele frequencies that occurs in small populations

gene mutations

changes in a single gene

infrequent, but inevitable

can be deadly, neutral, or beneficial

natural selection

a natural process resulting in the evolution of organisms best adapted to the environment

for example, green grasshoppers can be easily seen by birds, so they adapt so that more grasshoppers inherit the brown color gene (survival of the FITtest)

reproductive capacity

all populations have the ability to increase in number, but they can't increase indefinitely

reproductive competition

if the population becomes too big, individuals will end up competing for resources within their environment because the ability of any environment to support a population is always finite

what are the three possible outcomes of natural selection?

- a shift in the range of values for a given trait in the same direction
- stabilization of an existing range of values
- disruption of an existing range of values

directional selection

natural selection where one specific, extreme trait is favored above all the other traits

stabilizing selection

natural selection favoring the common, or intermediate traits

disruptive selection

natural selection favoring the extreme or uncommon traits

sexual selection

natural selection favoring the traits that maximizes the efficiency of reproduction

bottleneck effect

an extreme example of genetic drift where most of a population is destroyed likely due to a disaster, left w/a small gene pool

founder's effect

usually due to immigration where organisms migrate to form new populations with small numbers, reducing genetic variety, leading to incest

define "species"

a group of interbreeding natural populations that can breed successfully

what are the three ways speciation can occur

- genetic drift
- mutation
- natural selection

define "speciation"

the formation of new species

give reasons why morphological traits may not be useful in distinguishing species

- members of the same species might appear different due to environmental conditions (think: humans and race)
- morphology can vary with age and sex (sexual dimorphism)
- different species can appear identical (cryptic species)

genetic divergence

when populations split into two or more due to different genetic changes, gene flow counters this

reproductive isolation

condition in which a reproductive barrier keeps two species from interbreeding, therefore creating genetic divergence

prezygotic isolation

mating or zygote formation is prevented (before zygotes form)

postzygotic isolation

after sperm + egg fuse (after zygotes form)

what are the prezygotic mechanisms

ecological isolation
temporal isolation
behavioral isolation
mechanical isolation
gametic isolation

ecological isolation

species occur in the same area, but they occupy different habitats and rarely encounter each other (utilize different resources in the same place)

temporal isolation

when two populations breed at different times

behavioral isolation

isolation caused by differences in courtship or mating behaviors (signals/preferences)

mechanical isolation

reproductive parts just don't fit together

gametic isolation

when sperm can't fertilize the eggs

geological isolation

physical separation of populations of organisms from one another due to geographical barriers

zygotic mortality

when egg and sperm fuse, but resulting zygote can't survive + dies

hybrid inviability

the zygote is formed and born but dies soon after due to a barrier

hybrid sterility

hybrid offspring mature but are sterile (infertile) as adults

mechanisms of speciation

- allopatric
- sympatric
- parapatric

allopatric speciation

the process of speciation that occurs with geographic isolation

sympatric speciation

the process of speciation that occurs with behavioral isolation

macroevolution

large-scale evolutionary changes that take place over long periods of time (microevolution + time)

stratification

the process in which sedimentary rocks (where fossils are found) are arranged in layers

morphological divergence

change from the body form of a common ancestor

produces homologous structures

example: turtle and tortoise

morphological convergence

individuals of different lineages evolve in similar ways because they faced similar environmental pressures

produces analogous structures that serve similar functions

example: shark and dolphin

comparative development

comparing the embryological development of organisms

basically, all organisms look the same as a fetus lmfao

similarities may be clues to evolutionary relationships

biochemical comparisons

comparing proteins, dna, rna, and enzymes

the kind and number of biochemical traits that species share is a clue to how closely they're related; more similarity = more related

taxonomy

science of classifying, naming, and identifying organisms

binomial nomenclature

genus name, single letter, uppercase

species name, full, lowercase

all in italics (**)

H. sapiens

what are the classes in classification?

kingdom, phylum, class, order, family, genus, species

big to small

five-kingdom scheme

monera, protista, fungi, plantae, animalia

three domains

bacteria, archaea, eukarya (protists, fungi, plantae, animalia)

archaea

a domain of unicellular prokaryotes that live in the most extreme environments due to their strong cell membrane

bacteria

a domain of unicellular prokaryotes that are usually the common infections

eukarya

a domain consisting of all organisms that have a nucleus (eukaryotic)

protista

a kingdom of mostly one-celled eukaryotic organisms that are different from plants, animals, bacteria, and fungi

amoeba, mold, algae

fungi

a kingdom of heterotrophs (decomposers) that obtain energy from dead organic matter

mushrooms

reason why world isn't covered in dead stuff

plantae

a kingdom of photosynthetic autotrophs

trees, flowers, grass

animalia

a kingdom of complex, multicellular organisms that lack cell walls, can usually move around, and quickly respond to their environment.

node

when a single lineage divides into two

root of tree

common ancestor

taxon

a group of species without a name

differential survival

individuals with favorable characteristics tend to survive more

sexual dimorphism

differences in the characteristics between genders of the same species

example: sexual organs, ability to grow more hair, mature faster

adaptive radiation

a process that produces new species from existing lineages

gradualism

the theory that evolution occurs slowly but steadily

punctuated

where a species undergoes changes very rapidly and then stops evolving for a long period of time

cladogram

diagram that shows the evolutionary relationships among a group of organisms

shows what each has in common or doesn't have in common

think the t-rex chicken game

phylogenies

the branching patterns of evolutionary relationships

common ancestor then brances
like the nova missions

stasis

standing still, stopped evolving for long periods of time

what is the impact of mass extinctions on the diversity of life?

mass extinctions reduce diversity by killing off specific lineages, and with them, any descendent species they might have given rise to

basically cuts a big branch off a small tree

why does genetic diversity increase population survival?

allows species to adapt to future environmental changes and avoid inbreeding

vestigial

things that organisms have but don't need

appendix

reversal

when species evolve back to structures they used to have

if humans went back to having more verical jaws