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- broad pattern of evolution over a long period of time
- origin of new species
- changes in life on Earth that is revealed by fossils
4 stages that produced first cells
- 1. abiotic synthesis - amino acids and nucleotides formed from lightening, UV radiation, or chondrite
- 2. The second stage is the fusion of these small molecules into macromolecules & proteins
- 3. protobionts- membrane-like structure/ makes outside environment diff from inside
- 4 .the self-replication of these molecules
When did earth and life form? Early earths conditions?
- Earth- 4.6 billion years ago
- Life- 3.9 - 3.8 billion years ago
- after showering of rocks slowed down the atmosphere was thick & contained gases like ammonia methane hydrogen CO2 Nnitrogen and water (some came from volcanic eruptions)
They were a solution of organic molecules in the ocean from which life began.
- Heat: water can evaporate faster & speeds up reactions
- Lightening: causes the chemical reaction that forms amino acids
- O2 free environment: compounds can bond b/c its not taking their electrons
Supporting evidence of MillerUrey Experiement
the chemical composition of meteorites and chondrites. A chondrite that was found in Australia in 1969 had more than 80 amino acids in it, which are the first step to production of the first cells.
What is an amino acid?
building block for protein / life
What is a nucleotide?
- they link together to form RNA and DNA
- determine genetic structure
Why is RNA 1st genetic material?
- its like a template for proteins
- its single strand of genetic information
- molecules in soup stick to each other & form RNA
- RNA can fold so it was able to make copies of itself (ribozymes make copies)
- DNA is to complicated to be first
Why did switch form RNA to DNA occur
- RNA wasn't stable, it was a guide for DNA
- DNA is more stable to hold genetic info
- RNA mutations occur more & DNA replicates more accurately
- DNA less likely to have mutations because it is double stranded
Define Fossil & Strata
- The remains of traces of organisms found in sedimentary rocks
- plants, animals, footprints
compressed layers of rocks which form when new layers of sediment rocks cover the older ones and are compressed. contains fossils
- Top layer- younger rocks 2/ more recent fossils
- Bottom: older rocks w/ older fossils
- extinction was a common occurrence
- opposed evolution
- Catastrophism: Periodic catastrophes destroy populations, areas are repopulated by species from elsewhere
- Explained changes in geographic features occurred gradually
- Example: weathering away of a canyon by a river
uniformitarianism: Took Hutton’s theory of gradualism and applied it to living things
Hutton & Lyell influenced Darwin- slow events can make biological change
- Life evolves as environment changes
- use & disuse: parts of the body used more grow others fade
- inheritance: acquired characteristics are passed to offspring
Adaptation is when organisms develop or modify certain characteristics to improve their survival and reproduction in particular environments. An example would be how the finches’ beaks adapted to the foods that were in their surroundings, like how a seed-eater has a large beak to crack seeds and pick them up.
- Artificial selection is the process in which humans modify species over generations by selecting and breeding individuals that possess preferred traits.
- human caused evolution
- use variations in populations to create vastly different “breeds” & “varieties”
Darwin's observation of nature (4)
- 1. Members of a population frequently vary greatly in their traits.
- 2. Traits are inherited from parents to offspring.
- 3. All species are capable of producing more offspring than their environment can hold.
- 4. Due to lack of food or other resources, a lot of these offspring do not survive.
- Inferences: individuals w inherited traits get higher probability to survive and reproduce and give leave more offspring
- ability to survive and reproduce lead to the accumulation of favorable traits
Evidences of evolution
- Direct observations of evolutionary change
- Fossil record: show the evolutionary modifications that have happened over time. A record showing us that today’s organisms descended from ancestral species
- Biogeography: is the geographic distribution of species. (when continent split up)
Evidence: Homologous Structures
- Homologous structures -similarities in characteristics resulting from common ancestry
- Similar structure, Similar development, Different functions, Evidence of close evolutionary relationship (recent common ancestor_
Evidence: Analogous Structures
- Separate evolution of structures
- similar functions
- similar external form
- different internal structure & development
- different origin
- noevolutionary relationship
Evidence: Convergent Evolution
- Convergent evolution: an independent evolution of similar features in different ancestries
- evolved similar “solution” to similar “problems"
- Parallel Evolution: Convergent evolution in common environments
- filling similar ecological roles in similar environments, so similar adaptations were selected
- but are not closely related
Evidence: Vestigial strucutres
- Modern animals may have structures that serve little or no function
- remnants of structures that were functional in ancestral species
- deleterious mutations accumulate in genes for non-critical structures withoutreducing fitness ex: Hind leg bones on whale fossils
Evidence: Comparative embryology
- Similar embryological development in closely related species
- all vertebrate embryos have similar structures at different stages of development
Evidence: Molecular Genetics
- Closely related species have sequences that are more similar than distantly related species
- DNA & proteins are a molecular record of evolutionary relationships
- Comparing DNA & protein structure, universal genetic code! DNA RNA
- compare common genes
- Structures that carry genetic information
- made of DNA & proteins
A form or version of a gene
A Gene's specific location along a chromosome
A form of hereditary units that contain coded genetic info from parents
- AA or Aa
- determines an organisms appearance
- it has no notable affect on the organisms appearance
An organism that has a pair of identical alleles
An organism that has two diff alleles for a gene
Measure Genetic variability
Average heterozygote (average % of loci that are heterozygous )
- a change in the nucleotide sequence of an organisms DNA
- produces variation in alleles
- can invent new alleles
- new alleles can provide a selective adavantage
- impact phenotype
- can provide better match for environment so they can reproduce
- differences in genetic composition of seperate popualations
- evolve from isolation from one another
- happen b/c of chance events (drift)
Describe two events that increase genetic variation in a species.
- Mutations: provide new source of alleles
- result in new appearance
- duplication errors in genes continyue over genterations and mutations build up & species evolve
Sexual Reproduction: combination of alleles from individual species determine a new individual genotype
What is a population?
a group of individuals of the same species that live in the same region and interbreed
What does it mean if we say a population is in Hardy-Weinberg equilibrium?
pop.s gene pool is not evolving so it is remaining constant. there will continue to be the same genotype frequencies
List the five conditions that must exist for a population to exist in Hardy-Weinberg equilibrium.
- No mutations b/c it provide genetic variation
- Random mating individuals interbreed and keep genotype frequencies the same
- No Nat Selection b/c changes allele frequencies
- large population no genetic drift the smaller the more likely there will be gene change
- no gene flow pop is isolated from other ones b/c when alleles move from gene pool vartation can occur
Define genetic drift.
- random increase or decrese of alleles
- happens w small pops
- chance evetns cause a change in allele frequencies
2 types of genetic drift
Founder effect: alleles are transfered to another area b.c of chance (genetic drift) then new pop is formed ex: all of the "blue-skinned" residents can trace their ancestry to one couple, who were among the original settlers of this region.
Bottle neck: when pop undergoes a dramtic decrease in size (b/c of cnahce event) the small pop only has little variation bc some alleles were lost. The pop recovers in size bt there is not as much variation
How does Nat selection & genetic drift change allele frquency?
Nat selection changes allele frequenceis b/c the alleles that are not selected against will increase in frequency. that allele is favored so adaptive evolution occurs and and they become a better match for their environment
Genetic Drift changes allele frequencies by chance. ex: one gets stepsed on and dies so thet other alleles increase in frequency
What is relative fitness? How is it relevant to natural selection?
- the contribution an individual contribute to the gene pool.
- ability to survive and reproduce
- relative fitness contributions come about because the organism has an adaptive advantage that nat selection acts on.
- favors traits that are one extreme trait of the popluation traits opposite of this are acted against.
- frequncy goes one way or another
- diversifying slection
- occurs when environement favors both extremes
- acts agaisnt common traits
- favors the intermediate varitants and acts against extreme traits
- favors common trait
- heterozygote advantage
mechanisms tha preserve genetic variation
Diploidy: two copies of each chromosome. genetic variation is hidden in heterozygotes, the recessive allele is hidden so it isnt acted against. variation is stored for later generations
Balancing selection: when 2 traits or forms of a pop are maintained (instead of the dominant ONE)
Heterozygote advantage: imtermediate and both homos are preserved in pop. / heterozygotes have greater fitness than the two homozygotes ex: malria resistant gene
Frequency dependant selection: favors the pheontype that is less favored/ common phenotypes are selected against b/c fitness declines when its too common
neutral variation: selection where there is no specific advantage b/c DNA variation doesnt effect fitness. change comes as a result of genetic drift.
why we have imperfect organs
- can only work w exisiting alleles
- doesnt act against fittest , it acts against those good enough to reproduce
- cant eliminate ancestral history and start form scratch
- there is compromise and chance involved
Micro vs Macro evolution
- micro: how pops cahnge from generation to generation & how new species come about
- Macro:pattern/ changes in species over period of time. the patterns determine relationships among species
biological species concept:
- ernest mayr
- a species is a group of populations whose members interbreed and produce viable and fertile offspring w memebers of their population
- PREVENT FERTILIZATION
- habitat isolation: species dont encounter one another b/c of physical barriers
- temporal: mate during different seasons or diff times of the day
- behavioral: species dont recognize other species mating call (courtship rituals) or scent
- Mechanical: when their genetilia are not compatable / morphological differences
- gametic: sperm can tfertilize egg / or cant survive in female
- prevent reproduction after hybrid is born
- Reduced hybrid viability: zygote fails to develop properly and dies before it can reproduce/ genes interact in diff eways and impair development
- Reduces hybrid fertility: ybrids can become adults but cant reporduce and are sterile (eggs dnt work) b/c chromosomes of 2 parent differ and cant pair correctly in meiosis
- Hybrid breakdown: hybrids produce offspring but they are sterile
- process where a species splits into 2 or more species
- formation of new species occurs by allopatric or sympatric selection
when pop is georaphically isolated
habitat differentiation, sexual selection , polyploidy (autopolyploid & allopolyploid)
- genetic variation allows some organisms to take advantage of a specific part of a habitat. then those develop into new species bc they have diff habitats & they evolve to adapt to it
- ex: maggot fly original habitat hawthorn tree & some colonized apple tree and those developed create new pop
- limits gene flow and they cnt mate w parent pop
- when males or females of the pop select their mates based on appearance & fitness
- mate choice can result in development of new species
- intersexual: Mate choice/ female choose mates / between sexes
- intrAsexual: same sex; competition for mates ; selection within the same sex ; individuals of one sex compete to mate with oppostie sex
- cell division (meiosis) that results in extra set of chormosomes that prevent the formation of viable offspring
- possesion of more than the normal two sets of chromosomes
- occurs in plants
: more than 2 sets of chromosomes that came from one species/ cant produce with other organisms b/c diff # of chromosomes
: fertile hybrids that were once sterile they can mate w each other bt not parent species; can reproduce asexually
- gradualism: Darwin and Lyell
- cant tell change in strata
- physical change takes long time; nig changes only seen after long periods of time
- species change gradually
- new species branch off from parent and dont show much change for the rest of their life
- sudden change that can be distinguished in strata
- rate of speciation is nonconsistant; rapid busts of change; no change for a while