BIO125 Cumulative Final Exam

Evolution

The process by which species change over time through genetic variation and natural selection, leading to adaptation and diversification of life forms.

Genetic mutations

random changes in DNA that introduce NEW TRAITS

gene flow

TRANSFER of genes between populations

genetic drift

RANDOM changes in gene FREQUENCIES, especially in small populations

natural selection

The process by which organisms better adapted to their environment tend to survive and produce more offspring. Advantageous traits become more common. Acts on phenotypes (observable traits) but relies on genotypes (genetic makeup) for inheritance. Examples: peppered moths, Darwin’s finches

two sources of genetic variation in a population

mutations and sexual reproduction (recombination)

mutations

Random chances in the DNA sequence of an organism. Ultimate source of all genetic variation

sexual reproduction (recombination)

the mixing of genetic material from two parents during reproduction, creating unique combinations of genes in offspring

describe Darwin’s postulates about natural populations

1. individuals in a population vary (differ in traits)

2. some trait differences are heritable

3. more offspring are produced than can survive (overproduction leads to competition for resources)

4. survival and reproduction are not random (individuals with advantageous traits are more likely to survive and reproduce, passing those traits to next gen)

species

Group of organisms that can interbreed and produce fertile offspring under natural conditions. Reproductively isolated from other such groups

how scientists identify different species

1. biological

2. morphological

3. ecological

4. phylogenetic

5. reproductive isolation

two ways species are formed

1. allopatric speciation

2. sympatric speciation

allopatric speciation

• geographic isolation

• population is physically separated by a geographic barrier (mountain, river)

• separated groups evolve independently thru mutation, natural selection, and genetic drift

• over time, groups become different —> forming different species

sympatric speciation

• no geographic isolation

• new species arise within same area, often thru genetic changes or ecological differences

• polyploidy

• behavioral isolation

• ecological isolation

behavioral isolation

changes in mating preferences

ecological isolation

populations exploit different resources

polyploidy

• common in plants

• an error in cell division doubles chromosome numbers

• creates reproductive isolation

prezygotic barriers

• prevent mating/fertilization from occurring in the first place

• act before a zygote is formed

• more efficient (no wasted reproductive effort)

• isolation barriers

• ex: behavioral isolation in birds

zygote

fertilized egg

habitat isolation

• populations live in different habitats

• two species of snakes: one lives in water, the other on land

temporal isolation

• breed at different times

• skunks that mate in the summer vs winter

behavioral isolation

• differences in mating behaviors or courtship rituals prevent mating

• ex: birds of paradise with elaborate dances

mechanical isolation

• physical incompatibility

• snails with shells that spiral in opposite directions cannot mate

gametic isolation

• sperm and egg cannot fuse due to biochemical or molecular incompatibility

• ex: sea urchins: sperm of one species cannot fertilize eggs of another species

postzygotic barriers

• act after fertilization and prevent the hybrid offspring from surviving or producing

• reduce fertility/hybrid viability

• less efficient (energy spent on non-viable offspring)

• hybrids…

hybrid inviability

• hybrid offspring fail to develop or survive to adulthood

• some salamander hybrids die before birth or shortly after

hybrid sterility

• hybrid offspring survive but are sterile

• mules (horse + donkey) are sterile

hybrid breakdown

first-gen hybrids are viable and fertile, but their offspring are weak or sterile

adaptive radiation

• a single ancestral species rapidly diversified into many new species

  • each adapted to exploit different ecological niches/environments

• rapid speciation

• common ancestry

• ecological diversity

• morphological and behavioral adaptations

rapid speciation

multiple new species arise in a relatively short geological time

common ancestry

all new species share a recent common ancestor

ecological diversity

species evolve to occupy a variety of niches (different habitats, food sources, or behaviors)

morphological and behavioral adaptations

new species develop distinct physical traits or behaviors suited to their environments

why variation is necessary for evolution

• This is the raw material of evolution

• it provides the raw differences that natural selection can act upon

• without this, populations would lack the diversity needed to adapt to changing environments, leading to potential extinction

• importance:

  • enables natural selection

  • drives adaptation

  • prevents extinction

  • facilitates speciation

  • maintains population health

sources of variation

• mutations

• sexual reproduction (recombination)

• gene flow

• horizontal gene transfer

• polyploidy

three modes of natural selection

1. directional selection

2. stabilizing selection

3. disruptive selection

directional selection

• favors individuals at one extreme of a trait’s distribution, shifting the average toward that extreme

• the mean (average) of the trait changes

• ex: peppered moths

stabilizing selection

• favors intermediate traits and acts against extreme phenotypes, reducing variation in the population

• less diversity in the trait

• ex: human birth weight (average birth weights have higher survival than very low or very high)

disruptive selection

• favors both extremes of a trait’s distribution while acting against intermediate phenotypes

• can lead to bimodal distribution and over time, speciation

• more diversity in the trait increases

• often occurs in heterogeneous environments where different extremes are advantageous in different contexts

• ex: lizard coloration

allele frequency

how common that allele is in the whole group

allele

specific version of a gene

genotype frequency

how common that genotype is in the whole group

genotype

genetic makeup of an organism, the specific combination of alleles

hierarchical organization of classification names (most inclusive to exclusive)

1. domain (most inclusive)

2. kingdom

3. phylum

4. class

5. order

6. family

7. genus

8. species/specific epithet (most exclusive)

“Dear King Phillip Came Over For Good Soup”

human classification (most inclusive to exclusive)

1. Eukarya

2. animalia

3. chordata

4. mammalia

5. primates

6. hominidae

7. homo

8. homo sapiens

“Every Active Caveman Must Protect His Hairy Hands”

phylogeny

• the evolutionary history and relationships among species or groups of organisms

• shows how species have descended from common ancestors over time

• tracing trait evolution

• studying biodiversity and speciation

• prediction of characteristics

• understanding disease evolution

phylogenetic tree

• diagram that represents species’ relationships

• branches

• nodes

• branch lengths

• sister taxa

branches

shows lineages evolving over time

nodes

representing common ancestors

branch lengths

sometimes indicating genetic change or time

sister taxa

• two groups that share an immediate common ancestor

• each other’s closest relatives

• branch off from the same node on the tree

evolutionary history of prokaryotes

• spans over 3.5 billion years

• the oldest and most abundant life forms

• origin of them (no oxygen)

• photosynthetic and oxygen revolution (cyanobacteria)

• endosymbiotic theory and rise of eukaryotes (2.0 billion years ago)

• diversification and adaptation (complexity)

prokaryotic cell

• no nucleus

• small size

• no organelles except ribosomes

• circular, no histones

• binary fission

• peptidoglycan (bacteria) cell wall

• simple flagella

• ex: bacteria, archaea

eukaryotic cell

• membrane-bound nucleus

• large in size

• organelles (mitochondria, ER)

• linear structure, wrapped in histones

• mitosis/meiosis

• cell wall: cellulose (plants), chitin (fungi), none (animals)

• complex, microtubule flagella

• ex: animals, plants, fungi, protist

Four structures that all living cells possess

1. DNA

2. ribosomes

3. cytoplasm

4. plasma (cell) membrane

different shapes of bacteria cells

1. coccus (spherical)

2. bacillus (rod-shaped)

3. spirillum (spiral-shaped)

Di, Strepto, Staphlo

1. Di (pairs)

2. Strepto (long chains)

3. staphlo (grape-like clusters)

fimbriae (pili)

• hair-like, filamentous structures found on the surface of many bacteria

• shorter than flagella

flagella

long, whip-like structures (movement)

cell wall

structural support, shape, protection

DNA

carrier of genetic information

sex pili

hair-like, long, attachment for reproduction

capsule

protective gelatinous layer, composed of polysaccharides/polypeptides

endospore

resistant asexual spore that develops inside cell

plasmid

small, extrachromosomal DNA molecule

bacteria cell

Three primary functions of the cell wall

1. protection against external stress

2. structural support and shape

3. regulate cell growth and division

Gram-positive bacteria (+)

• thick peptidoglycan layer

• teichoic acids

• stains purple/blue

• ex: staphylococcus, streptococcus, bacillus

Gram-negative bacteria (-)

• thin peptidoglycan layer

• outer lipid membrane

• lipopolysaccharides (LPS)

• stains pink/red

• more resistant to antibiotics

• ex: E.coli, salmonella

binary fission

• asexual reproduction by prokaryotic organisms

• splitting into 2 identical daughter cells

Phototrophs

use sunlight as energy source

chemotroph

use chemical compounds as energy source

autotroph

use inorganic carbon (CO2) as carbon source

heterotroph

use organic carbon (glucose, amino acids) as carbon source

aerobic

• oxygen-RICH environments

• ex: soil, human body

anaerobic

• oxygen-POOR environments

• ex: deep soil, stagnant water

obligate

• strict oxygen rules

• must have specific conditions, otherwise cannot adapt

• ex: this aerobe must have oxygen

• ex: this anaerobe oxygen is toxic to them

facultative

can adapt to varying conditions

ex: this anaerobe can grow with or without oxygen

3 domains of life

1. bacteria

2. archaea

3. eukarya

“BAE”

kingdoms found within domain Eukarya

1. animalia

2. plantae

3. fungi

4. protista

APFP

characteristics of the Eukaryotic cell

• true, membrane-bound nucleus

• membrane-bound organelles

• complex cytoskeleton

• mitosis and meiosis

• linear chromosomes

• sexual reproduction (in most)

• larger cells

• contains cell wall (in some)

• endosymbiotic theory

• ex: humans, mushrooms, amoeba, yeast, oak trees

endosymbiont theory

1. free-living prokaryotic organisms were engulfed by larger host cell

2. engulfed prokaryotes lost independence and became permanent residents

   1. evolved into organelles, then into mitochondria

3. later, a cell already had mitochondria absorbed cyanobacterium thru phagocytosis

4. symbiotic relationship

   1. cyanobacterium provided glucose and oxygen, benefitting host

5. over time, cyanobacteria lost independence

   1. evolved into plastid, chloroplast

evidence (5) for evolution of mitochondria and chloroplasts in eukaryotes

1. own circular DNA (like bacterial DNA)

2. double membrane structure

3. independent reproduction (like bacteria)

4. ribosomes (like bacterial ribosomes)

5. gene transfer and shared genes (HGT)

derived traits of land plants

• cuticle

• stomata

• multicellular, dependent embryos

• alternation of generations

• sporangia

• apical meristems

• vascular tissue

• secondary compounds for chemical defenses

• protected gametes, pollen, seeds, flowers, and fruits

cuticle

waxy outer layer

stomata

pores on leaves

sporangia

• spore-producing structure

• spores found on the underside of fern leaves

• spores are dispersed by wind

vascular tissue

xylem and phloem

alternation of generations

• life cycle that alternates between two multicellular phases:

1. gametophyte

2. sporophyte

gametophyte

• haploid

• produces gametes (sperm and egg) via mitosis

sporophyte

• diploid

• produces spores via meiosis

apical meristems

• root - roots growing downward into soil

• shoot - stems and leaves growing upward toward light

gametangia

• antheridia - produce and release sperm

• archegonia - produce and protect the egg

flagellated sperm

• sperm have whip-like tails

• require water to swim to the egg for fertilization

• seed plants do not have flagellated sperm, instead produce pollen

leading phylogenetic hypothesis about relationship between all plant groups

1. transition from green algae to land plants (bryophytes)

2. evolution of vascular tissue (seedless vascular plants)

3. evolution of seeds (seed plants: gymnosperms and angiosperms)

4. evolution of flowers and fruits (angiosperms)

non-vascular plants

• bryophytes (mosses, liverworts, hornworts)

• pioneer species

• moisture retention prevents soil erosion

• no vascular tissue (lack xylem and phloem)

• no true roots

seedless vascular plants

• ferns, club mosses, horsetails, whisk ferns

• habitat creation (shelter)

• soil stabilization (prevent erosion)

• has xylem and phloem (plants grow tall)

• has true roots, stems, leaves

• sporangia on leaves

• spores no seeds

• has rhizomes (horizontal underground stems)

Gymnosperms

• seed plants (naked seeds)

• pine trees, spruce, fir, conifers

• seeds not enclosed in fruit, no flowers

• produce pollen and wood

• needle-like or scaly leaves

• wind pollination

• resin production

• cones are female

• well-developed xylem and phloem

• forest ecosystems, carbon storage, wildlife habitat

Angiosperms

• flowering plants

• seeds enclosed in fruit

• most diverse and dominant group of plants

• roses, oak trees, grasses, sunflowers, maple trees, fruit plants

• petals, stamens (male), and pistils (female)

• double fertilization

• short generation times (annual plants)

• coevolution with pollinators

seeds contain…

• embryo - the young plant

• endosperm - a food supply for the embryo (formed thru double fertilization)

• seed coat - protective outer layer