Evolution Exam 1

What is evolution?

Change in properties of groups of organisms over the course of generations.

Hypothesis vs. scientific theory

Hypothesis ( scientific fact) : may be poorly supported at first but it can gain support to the point that it is effectively a fact.

Scientific theory: Comprehensive, coherent body of interconnected statements, based on reasoning and evidence that explain some aspect of nature, or many aspects.

Pre- Darwinian Beliefs

• independent creation of life forms

• life forms did not change over time or from generation to generation. God created an infinite number of life forms. started from simple to complex.

• scientist described plants and animals without trying to explain why they go there.

TDR: Carl von Linne

• 1707- 1778

• Swedish botanist known at the father of taxonomy

• Developed a binomial system of nomenclature that nested classifications and did not imply evolutionary relationships

TDR: Georges Cuvier

• (1769- 1832)

• French anatomist known as the father of paleontology

• noted changes in fossil and deemed that fossils reflected extinctions and advocated catastrophism ( extinct species are replaced by new ones)

TDR: James Hutton

• 1726-1797

• Scottish geologist that purposed they theory of gradualism

  • geological changes occur slowly over time and still occur today ( accumulated effects)

TDR: Charles Lyell

• 1797- 1895

• British Geologist that purposed that the geologic processes of the past are the same as today (uniformitarism)

  • stratigraphy preserves the history of earth

  • geological processes take a long time

TDR: Jean- Baptiste de Lamarck

• 1744-1829

• French biologist who compared fossils of living species. He stated that each line of descent was a chronological series of older to younger fossils, leading to a mode species.

• two main principles

  • use and disuse of parts

  • inheritance of acquired traits

what is Lamarack-ism

principles include use and disuses and inheritance of acquired traits

• evolution reflects the innate drive of organisms to become more complex

• Giraffes obtaining longer necks to eat off of trees

Lamarck’s vs. Darwin’s hypothesis

Lamarck thought that evolution could happen within the lifetime of the individual. Darwin stated that evolution happens over a long period of time over several generations.

Charles Darwin

• 1809-1882

• English naturalist who after studying at Cambridge took a 5year voyage on the HMS Beagle where he studied specimens

how do adaptations arise

Natural selection

• individuals with certain inherited characteristics leave more offspring than individuals with other characteristics

Alfred Russell Wallace

• Studied organisms in amazon river basin, the Malay archipelago, and pacific islands.

• British Naturalist known as the father of biogeography

  • independently conceived the theory of evolution via natural selection in 1858 around the same time as Darwin

The origin of species

1959 Darwin published the origin of species which purposed

• organisms are related through descent from a common ancestor that lived in the past

• descendants accumulated diverse modifications that allow them to survive and reproduce

• over time, descent with modification led to the diversity of life we see today

what can descent with modification be represented as

an evolutionary tree

Darwin proposed natural selection as the mechanism of what

evolution

these views were mainly founded on artificial selection

Darwins observations of natural populations

1. members of a population vary greatly in their inherited traits

2. species are capable of producing more offspring than the environment can support, and some offspring fail to survive and reproduce

Darwins inferences of natural populations

1. individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment than other individuals then to leave more offspring than other individuals

2. this unequal ability of individuals to survive and reproduce will cause favorable traits to accumulate over generations

what are successful traits known as

adaptations

how are adaptations passed to the next generation

natural selection

true or false: individuals evolve

False, changes happen at the level of the population

True or false: natural selection acts only on heritable traits

true

True or false: traits are always useful

false, traits vary in different environments. some traits may be useless in a different environment.

what did Darwin mean by descent with modification

evolution

what was darwin’s and wallace’s most original concept?

natural selection

what is the tree of life

estimate of the relationships among all organisms on earth, that shows hypothetical phylogenetic relationships. It includes all species extant and extinct. it also reflects the historical process.

what is the phylogenetic theory

• Walter Zimmerman proposed

  • phylogenetic relationships is defined in terms of a shared common ancestry

why do we need to understand the tree of life

• human health: understand the evolution of many common diseases

• conservation: how many species are in the world?, distribution, biodiversity

• agriculture/ animal husbandry: plants and animals have been changing for centuries, often times looking genetic diversity. The tree of life helps us figure out ancestors

• invasive species: lion fish

What are the 5 kingdoms

plants, animals, fungi, protist, monera

what are the 3 domains of life

eukaryotes, archea, bacteria

What is systematics

started out as away to name things by placing them into categories, now it encompasses two disciplines

1. taxonomy: naming and cataloging organisms, often uses a code

2. phylogeny: unraveling its evolutionary history

What is taxonomy

formal system for naming and classifying species following the principle of common descent

• closer the group the more recent ancestry

• usually based on shared features

is systematics broad or narrow?

broader science of classifying organisms, it is based on studies of variation among populations that reveal their evolutionary relationships.

Who designed the current system of classification ( taxonomy)

Carolus Linnaeus

Linnaean taxonomy

• divided animal kingdom into species and gave each a distinctive name

• grouped based on shared common essential properties

• arranged in an ascending series of groups with increased inclusiveness

what are taxa

major animal groups at each level in the hierarchy and they indicate the general degree of inclusiveness

Kingdom, phylum, class, order, family, genus, species

What is binomial species nomenclature

two words

scientific name is written in italics or underlines

the first work is the genus and is CAPITSLIZED

the second is the specific epithet and is in lower case

what is a species

still unanswered to this day but there are specific criteria

• common descent: traces back to a common ancient population

• smallest distinct grouping: in smallest unit possible that shares ancestry and descent

• reproductive community: must be able to have fertile offspring

Cosmopolitan geographic range

very large range and worldwide distributions

endemic geographic range

very restricted geographic distributions

typological species concept

before Darwin, species were considered a distinct and immutable entity derived from divinely created patterns

Not common anymore as species are no longer views by certain morphological features

Biological species concept

a species is a reproductive community of populations ( reproductively isolated from each other) that occupies a specific niche in nature

ability to successfully interbreed is central to the concept

Problems with the biological species concept

• lacks an explicit temporal dimension

• disagreement on the degree of reproductive isolation necessary for considering two populations separate species

• boundaries between species may be difficult to locate

• interbreeding does not occur in asexual organisms, which only do binary fission and budding

Evolutionary species concept

• proposed by George gaylord Simpson in 1940s

• an evolutionary species is a single lineage of ancestor descendant populations that maintains its identity distinct from other such lineages and has its own unique evolutionary tendencies and historical fate

Advantages of evolutionary species concept

• accommodates sexual and asexual forms as well as fossils

• adds evolutionary time dimension

  • allows unbroken genealogical chain, sister species converge on their CA

what is the major goal of systematics

to infer the evolutionary tree or phylogeny that relates all extant and extinct species

what does phylogenetic analysis depend on

finding shared features among organisms that are inherited from a common ancestor

Homology

character similarity resulting from common ancestry

Homoplasy

non homologous similarities that may be found in various organisms

• arrise from convergent evolution or character reversals

what is a character

observable feature thought to he homologous across species of interest

what is a character state

alternative conditions of the character

outgroup vs ingroup

Outgroup: group that is phylogenetically close but not within the group being studies

Ingroup: in the group being studied

Clade

unit of evolutionary common descent that includes ancestral lineage and all descendants

synapomorphy vs symplesiomorphy

Syn- derived character shared by members of a clade and used as evidence of homology, helps infer that a particular group of organisms forms a clade

sym- sharing of ancestral states

apomorphy- derived in one taxon

what characters are useful for constructing cladograms come from

1. comparative morphology: examines shapes, sizes, and development of organisms. living specimens and fossils are used

2. cytology: looks at number, shape, size of chromosomes. only really used in living specimens

3. biochemistry: looks as AA sequences in NA

Relationship between taxonomic group and phylogenetic tree can take one of three forms

1. monophyly- most recent common ancestor and all descendants of that ancestor

2. paraphyly- most recent CA of all members of a group and some but not all descendants of that ancestor

3. Polyphyly- does not include the most recent CA of all members of a group. the group has at least two separate evolutionary origins

what is convexity

Mono and paraphyletic groups share this property and it helps distinguish it from polyphyletic groups.

• a group is convex if you can trace a path between any two members of the group on a cladogram without leaving the group

Phylogenetic systematics does what

1. accepts monophyletic groups

2. rejects polyphyletic and paraphyletic groups

what are the 5 mechanisms of evolution

1. Mutation

2. gene flow

3. sexual selection

4. natural selection

5. genetic drift

Natural selection

any consistent difference in fitness among phenotypically different biological entities

what are the 4 conditions of natural selection

1. variation- individuals differ

2. inheritance- traits are passed on

3. differential survival & reproduction ( fitness)

4. time- changes accumulate over generations

what are sources of variation

mutation, recombination, gene flow

inheritance

traits must be inherited, not acquired

• offspring tend to resemble their parents

why might harmful alleles persist in differential survival and fitness

1.mutation selection balance

1. new harmful mutations continually arise

2. selection removes them, but as long as mutation rates are high enough, some will always remain in the population

2.Genetic drift

1. in small populations, chance events can maintain or even increase harmful alleles, despite being disadvantageous

3.Context dependent fitness ( changing environments)

1. an allele that is harmful in one environment may be helpful in another

Levels of natural selection

Gene, individual, groups, entire species

gene level selection

• genes that increase their own transmission

• genes spread even if not always beneficial to the organism

• ex. transposable elements ( jumping genes)

genes compete to replicate

individual level selection

MOST COMMON LEVEL

• acts on traits that increase an individual’s fitness

• ex. faster gazelles are more likely to survive predators and reproduce

Main driver of selection

Kin selection

• individuals help relatives boosting shared genes

• may reduce personal fitness but increases kin survival

• ex. worker bees helping queen reproduce

• altruism

group level selection

• selection may act on groups wit cooperative traits

• groups that cooperate may outcompete those that do not

• Ex. bees are cooperative social animal groups that tend to survive better

species level selection

• acts on traits that affect he entire species survival or speciation

• species with wider ranges or flexible diets may persist longer

• macroevolutionary perspective

• traits affect long term persistance

adaptation

• inherited trait that increases fitness

• can be morphological, behavioral, physiological

exaptation

features that evolved in the past under different conditions and now serve new or no function at all

The nature of adaptations ( not all traits of organisms are adaptations)

1. traits may be consequences of physics or chemistry

2. traits may have evolved by genetic drift

3. traits may have evolved because they were correlated with other traits that were adaptive

4. traits may be consequences of phylogenetic history

what is a mutation

permanent change in DNA sequence of an organism.

• can occur in coding and non-coding regions

• if they occur in somatic cells they only affect that individual

• if they occur in germline cells they can be passed on and enter the populations gene pool

point mutation

chemical changes in just one base pair of a gene, 2 kinds

• insertions and deletions- additions or losses of nucleotide pairs in a gene

  • more harmful that substitutions

  • can alter reading frames producing a frame shift mutation

• substitutions- replaces one nucleotide with its partner

  • silent- no effect

  • missense- code for a AA but not the correct one

  • nonsense- change AA to a stop codon

what is it called if a mutation has an adverse effect on the phenotype of the organism

it is called a genetic disorder or a hereditary disease

alterations of chromosome structure

Breakage of chromosomes can lead to 4 types of changes

1. deletion- removes a chromosomal segment

2. duplication- repeats a segment

3. inversion- reverses the orientation of a segment within a chromosome

4. translocation- moves a segment from one chromosome to another

causes of mutations

1. spontaneous- errors in DNA replication and spontaneous chemical changes

2. Induces- exposure to external factors known as mutagens

rates of mutation

probability that a mutation occurs per gene, per cell division, or per generation

• mutation rates directly influence genetic variation, human disease, and the pace of evolutionary change

high vs low mutation rates

high- good for adaptability in changing environments but risky because most mutations are harmful

Low- good for stability and preserving well adapted genomes but risky if the environment changes and new adaptations are needed

mutation selection balance

harmful alleles arise continually by mutation but are removed by selection, maintaining a steady state.

consequences of mutation

1. molecular effects:

   1. neutral- no effects on fitness, most mutations

   2. beneficial- rare, but crucial for adaptation

   3. deleterious- can cause genetic diseases

2. Population effects: raw material for evolution, without no new ales arise. Natural selection, genetic drift, and migration all act on this variation, but they do not create it.

Other sources of variation

1. independent assortment: homologous pairs of chromosomes orient randomly at metaphase I of meiosis. 2^n

2. recombination: crossing over produces recombinant chromosomes which combine DNA inherited from each parent.

3. random assortment: random fertilization

mutation selection balance

evolution is a balance between mutation(introducing new alleles) and selection (removing harmful ones).