evolution

evolution

evolution

change over time in the genetic composition of a population; descent with modification

linnaeus

founder of taxonomy; binomial nomenclature

Domain, kingdom, Phylum, class, order, family, genus, species

(dear king philip came over for good spaghetti)

classification based on anatomy and morphology

cuvier

paleontologist-studied fossils

deeper stata (layers) very different fossils from current life

opposed idea of evolution

catastrophism - catastrophe destroyed many living species then repopulated by immigrant species

hutton

geologist

gradualism- geologic change results from slow and gradual continuous process

lyell

geologist

uniformitarianism- earth’s processes same rate in past and present (are constant) therefore earth is very old

lamarck

published theory of evolution (1809)

compared living species with fossil forms, found several lines of descent

use and disuse: parts of body used - bigger and stronger

inheritance of acquired characteristics: modifications can be passed on

organisms have innate drive to become more complex

malthus

english cleric and scholar, influential in the fields of political economy and demography

more babies born than deaths

consequences of overproducing within environment = war, famine, disease

struggle for existance

charles darwin

(1809-1882) english naturalist

1831-1836 - joined the ITMS Beagle for a 5 year research voyage around the world

collected and studied plant and animal specimens, bones and fossils

notable stop: Galapagos Islands

alfred russell wallace

published paper on natural selection first (1858)

overproduction

populations produce more offspring than can possibly survive leading to competition

natural variation

individuals in a population vary extensively from each other, mostly due to inheritance

fitness

struggle to survive; individuals whose inherited characteristics best fit to environment leave more offspring than less fit

adaptation

enhance an organism’s ability to survive and reproduce

descent with modification

unequal ability of individuals to survive and reproduce leads to gradual change in populations, with favorable characteristics accumulating over generations

Darwin’s theory of natural selection points

1. over production

2. natural variation

3. fitness

4. adaptation

5. descent with modification

evidence supporting evolution

fossil record, anatomical record, molecular record, artificial selection

homologous structures

similar structure, similar development, different functions

similarities in characteristics resulting from common ancestry

analogous structures

separate evolution of structures, similar functions, similar external form, different internal structure and development, different origin, no evolutionary relationship

convergent evolution

evolved similar solution to similar problems

filling similar niches in similar environments so similar adaptations were selected

analogous structures

vestigial organs

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 without reducing fitness

microevolution

a generation to generation change in a population’s frequencies of alleles

two main causes are genetic drift and natural selection

genetic drift

change in population’s allele frequencies due to chance

bottleneck effect

Disasters such as earthquakes, floods, droughts, and fires may reduce the size of a population dramatically

the surviving population may not be representative of the original population’s gene pool

founder effect

occurs when a few individuals from a larger population colonize an isolation island, lake or some other habitat

the smaller the sample size, the less the genetic makeup of the colonist will represent the gene pool of the larger population they left

natural selection

alleles pass on from one generation to the next due to some variants leaving more offspring than others

gene flow

genetic exchange due to migration of fertile individuals or gametes between populations (reduces differences between populations)

mutations

causes a change in DNA. can only lead to evolution and natural selection if the mutation is in the gametes

polymorphism

when 2 or more forms of a discrete character are represented in a population (skin color)

geographic variation

differences in gene pools between populations or subgroups of populations; can occur in different populations or within a population

cline

a graded change in some trait along with geographic axis (altitude)

darwinian fitness

the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals

relative fitness

the contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus

directional selection

shifts the frequency curve for variations in some phenotypic character in one direction or the other by favoring what are initially relatively rare individuals that deviate from the average for that character

diversifying/disruptive selection

occurs when environmental conditions are varied in a way that favors individuals on both extremes of a phenotypic range over intermediate phenotypes

stabilizing selection

acts against extreme phenotypes and favors the more common intermediate variants

speciation

the origin of new species

species

a population or group of populations whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot produce viable, fertile offspring with member of other species

reproductive isolation

each species if isolated by factors (barriers) that prevent interbreeding

prezygotic barriers

impede mating between species or hinder fertilization of ova

• habitat isolation

• behavioral isolation

• temporal isolation

• mechanical isolation

• gametic isolation

habitat isolation

two species living in different habitats within the same area will not encounter one another

behavioral isolation

special signals used by a species to attract mates

temporal isolation

species that breed during different times of the day, season, or year

mechanical isolation

structural differences in genitalia or flowers

gametic isolation

male and female gametes fail to attract each other or are unviable

postzygotic barriers

prevent the hybrid zygote from developing into a viable, fertile adult

creates a zygote that is not viable or fertile

• reduced hybrid viability

• reduced hybrid fertility

• reduced breakdown

reduced hybrid viability

hybrid zygotes fail to develop or fail to reach sexual maturity

reduced hybrid fertility

hybrid fails to produce functional games (mules)

hybrid breakdown

offspring hybrids have reduced viability or fertility (1st generation works, 2nd doesnt)

modes of speciation

allopatric, adaptive, sympatric

allopatric speciation

geographic barrier

interbreeding between two resulting populations is prevented

barriers include rivers to mountain ranges

gene flow is interrupted because they are separated in space

gene flow then diverges

sympatric speciation

formation of a new species without the presence fo a geographic barrier

gene flow is reduced due to chromosomal changes and nonrandom mating

in plants: autopolyploids (more than 2 chromosome sets) and allopolyploids (hybrids of two different spevies with more than 2 chromosome sets)

in animals: genetic factors could cause daughter populations to become dependent on resources other than the parent population

divergent evolution

two or more species originate from a common ancestor

convergent evolution

when unrelated speceis live in the same environment, subjected to the same selective pressures and develop similar adaptations

macro evolution

level of change evident over the time scale of fossil records (mass extinction)

morphological transformations

the evolution of complex structures from simpler versions (eyes)

punctuated equilibrium modell

paleontologists rarely find gradual transitions of fossil forms. they often observe species appearing as new forms rather suddenly in a layer of rock, persisting essentially unchanges, and then disappearing from the fossil record as suddenly as they appeared

species diverge in spurts of rapid change

species selection

species that endure the longest and reproduce the most offspring determine the direction of major evolutionary trends

phylogeny

evolutionary history of a species or group of related species

systematics

study of biological diversity in an environmental context

taxonomy

science of naming, identifying, and describing diverse forms of life

pangea

supercontinent of land masses

early atmosphere

the precambrian atmosphere was composed mainly of nitrogen and carbon dioxide. also had some methane and ammonia. volcanoes released water, carbon monoxide, and even more nitrogen and co2. no free oxygen

origins of life

the joining of monomers produced polymers with the ability to replicate, store, and transfer information

oparin/haldane hypothesis

1920s - primitive earth: volcanic vapors (reducing atmosphere which means electron adding) with lighting and UV radiation

this will enhance complex molecule formation

haldane coined the phrase primitive soup because he suggested the oceans were a solution of organic molecules from which life arose

miller/urey experiment

1953 - water, hydrogen, methane, ammonia, all 20 amino acids, nitrogen bases, and ATP formed, but no organic molecules

evidence suggests that the atmosphere was probably not reducing or oxidizing (electron removing)

possible that just areas around volcanic opening were reducing in order to create molecules

fox eperiment

1959 - suggested that proteinoid formation (abiotic polypeptide spheres) occurs from organic monomers dripped on hot sand, clay, or rock

hot and dry conditions are needed followed by being dissolved in water

permian period

250 mya

90% of marine animals went extinct

8 out of 27 orders of permian insects did not survive

extinction occurred in less than 5 million years

Reasons: same time continents merged to form pangea (marine and terrestrial habitats disturbed), massive volcanic eruptions in Siberia (increase in co2 = global warming)

cretaceous period

64 mya

extinction of dinosaurs

killed more than half of marine species

exterminated many families of terrestrial plants and animals

reasons: the climate became cooler, shallow seas receded form continental lowlands, large volcanic eruption in india, a large comet or asteroid collided with earth

cladogram

a tree constructed from a series of dichotomies or 2 way branch points that represent a divergence of an animal from a common ancestor, the deeper the branch to greater the divergence