BIO 201 evolution

Evolution by natural selection

Independent discovery in mid-19th century by Charles Darwin and Alfred Russel Wallace

Plato's theory of forms

A perfect version of everything exists, the world has the imperfect versions

Natural theology

Earth is young (~6000 years old); all living things were created by God and fit in the Scala Naturae; species do not change.

Watchmaker argument

Bishop William parley (1743-1805) organisms are complex and well adapted because they were made by God.. proof of God from complexity of life

Catastrophism

An idea that incorporated religion into the growing fossil record

Multiple layers of fossil species found, many of which no longer exist, layers closer are increasingly similar to modern species

Multiple divine catastrophes followed by creation events in a short period. God created variation on a general body plan with each new creation

Fossil record

What suggested that

1) different species appear over time

2) the world may be older than thought

Uniformitarianism

Forces acting on the earth were the same in the past as they are in the present, no divine events needed to create current earth... because change is slow the earth must be very old (aka gradualism)

Gradualism

Another name for uniformitarianism, change occurs slowly over time

James Hutton

Originated the idea of uniformitarianism

Charles Lyell

Authored 'Principles of Geology' which was highly influential, made the idea of uniformitarianism more well known

Principles of Geology

Darwin read this work during his travel as a naturalist on the HMS Beagle

Lamarkian Evolution

Spontaneous generation produces simple species that evolve over time due to:

Drive towards complexity and adaptive force

Thomas Malthus

wrote Essay on the Principles of Population which contained observations on human population growth (overpopulation concern) increases in food production cannot keep pace with growth which will lead to competition for food and not everyone will avoid starvation

** carrying capacity

Limiting factors

Population sizes generally do not change much because of food availability, space, predation, etc.

there is a struggle for existence between individuals in a population

Fitness

Some individuals will happen to be better suited to their environment than others, and so will be more likely to be among those that survive and reproduce

Evolution

A change in the genetic composition of a population over time

fitness (darwinian)

the ability of an individual to successfully reproduce

natural selection

a mechanism of evolution resulting from individuals with different traits showing differential fitness

adaptation

an increase in fitness due to evolution OR a trait that improves the fitness of an individual

genotype

the specific alleles or genes in an individual's genome

phenotype

the actual traits of the organism, resulting from a combination of genotype and environmental factors

monogenic trait (single-locus)

a phenotypic trait controlled by a single gene

polygenic trait (multi-locus)

trait influenced my multiple loci

populations species

evolution occurs at the level of ______________ or ________________

phenotypic selection

the component of the natural selection process in which some traits result in greater fitness than others

progressive

evolution is not inherently ...

genetic drift, gene flow, mutation

evolution can occur through means other than natural selection such as _____________, ________________, and ____________.

microevolution

changes within species, often involves single mutations and quantitative changes, may occur over one generation or thousands

macroevolution

the process of speciation and long term events, can involve major changes in form and function, may require millions of generations, but sometimes many less

rifampin

binds to RNA polymerase and interferes with transcription, stops metabolic processes (ability to make proteins)

rifampin resistance

bacteria that have a single point mutation in the gene rpoB that encodes part of RNA polymerase, prevents rifampin from binding

transitional forms

fossils that connect ancestral species with their descendants through a series of tiny steps

geographic distribution of species

evidence for macroevolution, Biological diversity results from the descendants of a local species migrating and adapting to new environments

taxonomic relationships

how species are related to one another in terms of evolution

homologous traits

Similar in structure, but does not have same function. They are inherited from a common ancestor.

vestigal traits

nonfunctional or greatly reduced traits

comparative approach

compare populations or species from naturally differing environments

experimental approach

actively manipulate the populations or environments to create differences

more

species that diverged more recently share _______ features than those that diverged longer ago.

directional selection

selection against one tail or another (of the curve), reducing variablilty

stabilizing selection

selects against both tails of distribution, reducing variability

disruptive selection

selects against center of distribution, increasing variability and creating bimodal pattern

balancing selection

frequency dependent selection occurs when rare phenotypes are favored

heterozygote advantage can also lead to this

fitness trade offs

morphological characters, physiological characters, biochemical characters, energy allocation

assortative mating

mate chosen based on similarity or dissimilarity to self

inbreeding

mate chosen based on close familial relationship

sexual selection

particular traits are more generally more attractive to mates

a different aspect of natural selection

homozygosity

inbreeding increases the likelyhood of...

sexual dimorphism

differences in phenotype of sexes, often due to sexual selection

• males become more showy and are more brightly colored

• occurs due to the fundamental asymmetry of sexes

intersexual selection

Selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice.

traits that show males have good traits, males that would provide good parental care

genetic drift

change in gene frequency due to chance

gene flow

movement of alleles from one population(source) to another (sink)

Fusion

Limited evolution has occurred, and gene pools remix. Groups may have genetically diverged but no reproductive isolation. Return to a single evolutionary group

Species remain distinct

Sufficient evolution for prezygotic isolation to occur

Hybrid zone

a geographic region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

Speciation through hybridization

If hybrids have as high or higher fitness than parents in some locations, and assortative mating or reproductive isolation occurs between hybrids and parental species, then hybrids may become a third species.

Reinforcement

Hybridization between divergent groups may produce less fit offspring or none at all (postzygotic isolation)

precambrian eon

period of time from the formation of the Earth (4.6 billion years ago) to the rise of life forms (hadean, archaean, proterozoic)

precambrian events

formation of earth 4.6 bya

origin of life (prokaryotic) 3.5 bya

oxygenic photosynthesis 2.7 bya

oxygenated atmosphere 2.2 bya

eukaryotic life appears 2 bya

multicellular life appears 1.5 bya

paleozoic era

the part of geologic time 570-245 million years ago ; invertebrates, fishes, amphibians, reptiles, ferns, and cone-bearing trees were dominant

paleozoic events

cambrian "explosion begins 560 mya

all major animal groups 520 mya

early plants invade land 480 mya

arthropods invade land 420 mya

vertebrates invade land 370 mya

first seed plants 360 mya

permian mass extinction 250 mya

mesozoic era

250-65 mya, first nectar drinking insects, first dinosaurs, first mammals, first flowering plant, first bee, first placental mammal (triassic, jurassic, cretaceous)

mesozoic era events

first mammals 180 mya

first flowering plants 155 mya

first birds 150 mya

cretaceous mass extinction 65 mya

cenozoic era

era that began about 66 million years ago, known as the "Age of Mammals"

cenozoic era events

primates appear 55 mya

apes appear 30 mya

human like apes appear 4 mya

adaptive radiation

rapid and extensive diversification of an evolutionalry group caused by open ecological niches and key adaptations

ecological niche

how an organism "makes a living"

key adaptation

A new feature that greatly improves the evolutionary potential of a group. can be morphological, physiological, behavioral, developmental, or genetic. allows the group to exploit a new habitat or lifestyle, or outcompete other groups.

cambrian explosion

rapid diversification of animal groups from simple forms (550 mya) occured over just tens of millions of years. appearance of: external and internal skeletons, cephalization, major sensory structures, locomotory appendages.

doushantuo fossils

from ~575 million years old chinese deposits, probably represent animal embryos, suggest organized developmental pathways producing complex forms

morphological species

based on the phenotype of individuals, original method for classifying species, carl linnaeus, binomial nomenclature

biological species

all individuals that can potentially interbreed to produce fertile offspring are considered a species, defined by reproductive isolation. can be due to prezygotic isolation or postzygotic isolation. ernst mayer in 1942

phylogenetic species

groups with sufficient separation on the phylogenetic tree are considered species

allopatry

"different countries", speciation through physical separation of populations

sympatry

"same countries", speciation through genetic divergence within a population

polyploidy

triploid or tetraploid individuals, reproductive isolation is typical dur to incompatible gametes

autopolyploidy

"self many-forms" an error in mitosis or meiosis leads to triploid (3n) or tetraploid (4n) individuals

allopolyploidy

"other many-forms" hybridization leads to mixed genome, duplication of chromosomes necessary for successful reproduction

reinforcement

matings between individuals from divergent groups may produce less fit offspring or none at all (postzygotic isolation) may be due to coadaptation of alleles within each population. unsuitability of intermediate phenotype for either environment

hybrid zone

hybridization leads to offspring with equal or higher fitness than parents, at least in some regions. may represent an intermediate environment, favoring an intermediate phenotype

mass extinctions

loss of many species across taxonomic groups, rapid occurrence (period over days or many years - think geological time scale), global scale

causes of mass extinction

global natural disasters

extraterrestrial impacts

abrupt climate change

phylogeny tree

Cretaceous mass extinction

Massive asteroid impact ~65 mya. Loss of 75% of terrestrial and marine species in complex pattern. Many reptile groups: dinosaurs, pterosaurs, marine reptiles, ammonoids, many insect species.

Iridium

What was present at high concentrations in rocks formed 65 million years ago that serves as evidence for an asteroid impact?

Permian Triassic mass extinction

"Mother of mass extinctions"

96% of marine species, all eurypterids (sea scorpions), trilobites. 70% of terrestrial species. Not sure of cause but possibly massive climate change, volcanism, or impact event.

Phylogeny

Evolutionary relationship among different groups

Monophyletic group

Consists of all the species sharing a single ancestral population

Paraphyletic group

composed of some but not all members descending from a common ancestor (missing some species)

Homology

If groups share a trait that is the same due to common ancestry it is a...

Homoplasy

If groups share a trait that is not due to common ancestry, it is _____

Often due to convergent evolution

Radiometric dating

Using half lives of radioactive elements to determine age. Organisms and minerals form with particular isotope ratios, over time some isotopes decay at a constant rate. Changes in isotope/elemental ratios reflect elapsed time.

Molecular clock

For some molecular characters, the rate of change is about as constant as radioactive decay. We can use fossil record to determine rate of molecular change.. (hemoglobin example)

Fossils

___________ allow us to reconstruct parts of the complete tree of life not seen in extant organisms, see what ancestral forms looked like, test genetically-generated trees against physical evidence, calibrate molecular clocks.

Improve

Factors that _________ chances of fossilization: hard body parts, habitat with still and or shallow water, large widespread population, more recent deposition.

background extinction

lower, average rate of extinction observed when a mass extinction is not occurring.

Vicariance

The physical splitting of a population into smaller, isolated populations by a geographic barrier.

Genetic diversity

The number and frequency of all alleles present in a species

Species diversity

The number and relative frequency of species in a particular region

Taxonomic diversity

The number of independent evolutionary lineages present