MBIO161 Exam

Two fold cost of sex

Sexual females produce half as many daughters as asexual females, resulting in asexual populations growing twice as fast if both produce the same number of offspring.

Isogamy

Identical gametes

Gametes

Specialized cells made by meiosis

Anisogamy

Non-identical gametes, often the smaller cell is male

Parthenogenesis

Asexual reproduction in which a female can produce an embryo without fertilizing an egg with sperm (ex. rotifers, insects, reptiles, amphibians)

Budding

Asexual reproduction where a new organism develops as an outgrowth, or "bud," from the parent organism (ex. baker’s yeast, hydra, anemones)

Binary fission

Asexual reproduction where a single cell divides into two identical daughter cells (ex. bacteria, protists & some unicellular fungi)

Fragmentation

Asexual reproduction where an organism splits into fragments, and each fragment develops into a complete, independent individual (ex. lichens, annelids, sea stars, plants)

Sex has been around for

1.2 billion years

Muller’s ratchet

Without recombination, deleterious mutations will accumulate

3 main advantages of sexual reproduction

It generates diverse offspring, eliminates costly mutations quickly and allows beneficial alleles to combine

Sexual dimorphism

The differences in physical characteristics between males and females of the same species

ZW system

Females (ZW), males (ZZ). Occurs in birds and some fish

Wolbachia

Intracellular parasites/endosymbionts (affects arthropods and nematodes). Tranmission through host egg but not sperm. Causes suppression of ‘male’ gene

Hermaphrodites

Frequent in invertebrates, occasional in vertebrates, usual in plants. Two types: sequential (ex. clownfish) and simultaneous (ex. garden snail)

Mitachondria are inherited

Maternally (mtDNA)

Reasons for flashier males

Traits are useful in male-male combat and traits preferred by females ‘secondary sex(ually selected) traits’

Parental investment theory (Trivers 1972)

The sex which exhibits less parental investment (not necessarily the male) will have to compete to mate with the opposite sex. In species where both sexes invest heavily, they should be mutually choosy.

Intra-sexual selection

Members of the same sex compete for mates

Inter-sexual selection

Females choose mates based on specific traits (ex. territory)

Sensory bias hypothesis

Female mating preferences may be by-products of selection on sensory systems; males evolve traits that “exploit” these biases

Fisherian runaway (1930)

Male ornamentation is the result of female preference for males with the most exaggerated ornaments; drives selection past the natural-selection optimum

Sexy son hypothesis

Assumes an indirect benefit to female choice due to the attractiveness of their sons. Females that mate with an attractive male will produce attractive sons (fitness will be increased as a result of their sons’ higher mating success)

Handicap principle (Zahavi 1975)

Reliable signals must be costly to the signaler (0nly high-quality individuals can afford the cost of the signal)

Hamilton-Zuk hypothesis (1982)

Special case of the Handicap principle; sexual ornaments are indicators specifically of parasite and disease resistance

Lek

Assembly areas for displaying to attract females

The lek paradox

There is a strong skew in male reproductive success; a few generations of mating should eliminate most genetic variation and yet females remain choosy

Co-adaptation

Complex adaptations involving multiple compatible changes at the same time (ex. cornea, retina, lens and shape in the eye)

Exaptation

A character that performs a different function to the reason it evolved (ex. bird feathers)

Spandrel

Side effects of adaptations (ex. large brain size in humans is (perhaps) an adaptation to foraging in a complex environment)

Constraints on adaptation

Genetic, historical, and developmental factors

Allopatric speciation

New species forms geographically apart from its ancestor

Cline

Gradient of continuous genotypic or phenotypic variation within a species

Ring species

A series of interconnected populations that gradually diverge in traits across a geographic range, forming a ring-like distribution

Peripatric speciation/isolation

A small population at the edge of the species range is isolated. Usually due to extreme conditions. This creates rapid evolution

Parapatric speciation

New species forms within a contiguous population (reinforcement occurs, but no physical barrier exists)

Stepped cline

A sudden change in the frequency of a gene or character across a geographic area (creates a step like formation on the cline)

Hybrid zones

Hybrid zones could indicate a parapatric speciation event. But could also be due to allopatric species meeting

Sympatric speciation

New species forms in geographical range of ancestor

Fossils are only found in

Sedimentary rocks

Permineralization

A type of fossilization where minerals deposited by water fill the internal spaces of an organism or tissue, forming an internal cast of the original structure

Radio-carbon dating

5730 years after death ½ the C14 → N14, only works for fossils up to 40,000 years

Volcanic ash dating

Many sediments contain volcanic ash (‘tephra’), potassium and argon decay more slowly than C14, only works fossils older than 100,000 years

Paleomagnetic dating

Age rocks by comparing the polarity of sediments to cores of rock from sea bed

Cretaceous

65-144 mya

Extinction of most dinosaurs, including bird-hipped (Triceratops) and lizard-hipped (T-rex) dinosaurs. Includes Sinosauropteryx with melanosomes in feathers.

Jurassic

144-206 mya

Quarry dinosaurs, very large herbivores, 4 species, up to 26m, est. weight 50-113 tons.

Triassic

206-251 mya

Includes Ichthyosaurs, marine reptiles that predated dinosaurs by 20 million years (went extinct just before the last dinsoaurs) and returned to the sea.

Permian

251-290 mya

Includes terrestrial tetrapods, arthropods, plants, fungi, fusulinids (protists with hard shells), and ammonites (molluscs with hard shells).

Carboniferous

290-354 mya

Coal deposits due to bark-bearing trees and high atmospheric oxygen (80% higher than today, allowing gigantism; giant insects

Devonian

354-417 mya

Lungfish, tetrapod colonization of land, first fossil insects & angiosperms, Rhynie chert fossils (plants and animals including oldest known terrestrial arthropod).

Silurian

417-443 mya

One of the earliest terrestrial plant fossils

Ordovician

443-490 mya

Nautiloids (shell-producing cephalopods with chambered, straight or curled shells; extant species)

Cambrian

490-543 mya

Trilobites (armored marine arthropods, earliest animal weapons, rapid evolution, 15000+ species, 9 orders); most animal classes appear.

Burgess shale

Cambrian deposits in the Canadian Rockies, discovered by Charles Doolittle Walcott in 1909.

Macroevolution

Speciation events or splits from a ‘lineage’

Mircoevolution

Changes within a species or within a ‘lineage’

Punctuated equilibrium

Evolutionary changes happen in short bursts away from the main population. These short bursts, rather than prolonged transitions, are missing from the fossil record

Phyletic gradualism-adaptation

An accumulation of new characters; Darwin’s meaning and compatible with punctuated equilibrium

Phyletic gradualism-pattern of evolution

Means evolution has a constant rate; not Darwin’s meaning and not congruent with punctuated equilibrium

Co-evolution

When two or more species directly influence each other’s evolution = exert selection pressure on each other

Mutualism

Prey exerts selection pressure on predator → predator exerts selection pressure on prey. Both evolve to have stronger/fitter traits

Miller-Urey experiment (1953)

Methane + ammonia + hydrogen → amino acids. Wrong mix of gasses and it required unrealistically high energy input

Bubble hypothesis

Waves drive oily bubbles (phospho-lipids) onto shore, forming primitive membranes enclosing nucleotides for UV exposure and organic polymer formation, where some replicate better.

Clay hypothesis

Silicate crystals in clay spontaneously 'replicate', attracting organic monomers and undergoing selection, eventually leading to self-replicating organic molecules.

Extra-terrestrial hypothesis

Organic compounds from space (ex. comets) seeded early Earth.

Mars hypothesis

Life may have originated on Mars due to its faster cooling, with complex organic polymers transported to Earth via asteroid impacts.

Gnathostomes

Vertebrates with jaws

Tetrapods

Gnathostomes with limbs and feet

Amniotes

Tetrapods with eggs adapted for land

Mammals

Amniotes with hair and lactation abilities

Primates

Eutherians (placental mammals) with hands and feet adapted for grasping

Anthropoids

Primates with a somewhat opposable thumb

Hominoids

Anthropoids with a fully opposable thumb – apes and humans

A. afarensis ‘Lucy’ (1974)

Discovered in Ethiopia, dating back 4.5-4.0 mya. Approximately 1m tall, Lucy was fully bipedal, a key adaptation in hominids. She had a small brain (400-500cc), tough-food diet adaptation with large jaw muscles, and a prognathus jaw, capable of only short-distance bipedal walking.

Australopithecus garhi (1999)

East Africa 2.5 mya. Larger chewing teeth ('Megadont'). First evidence of tool use and defleshing animal carcasses, suggesting that tool use may have evolved before large brain size. Bipedalism allowed selection on hands, improving dexterity and tool use.

Paranthropus spp. ‘Beside man’ (1938)

Robust australopith from Southern Africa, dating 2.3-1.2 mya, characterized by a sagittal crest.

Australopithecus africanus

Gracile australopith, 3.0-2.5 mya, Southern Africa. Bipedal, possibly arboreal.

‘Homo’ habilis ‘Handyman’

Lived 2.4 mya in Tanzania's Olduvai Gorge. With a brain size of 600-700cc, its classification is debated, and it may have had spoken language capabilities.

H. rudolphensis

500-800cc brain size, bigger wider, flatter face Lived 1.9 mya in Lake Turkana, Kenya. Large chewing muscles, but very little is known about this species.

Homo ergaster

1.5 mya, Kenya. Slender, fully bipedal with a large brain and low sexual dimorphism.

Homo erectus ‘Peking man’

Migrated out of Africa (first to do so) 1.5 mya, possibly a direct ancestor of modern humans. Extinct 0.2 mya.

Homo neanderthalensis

200,000-40,000 years ago. Similar to modern humans, replaced by H. sapiens in Europe (some interbreeding). Not direct ancestors of modern humans. Range: Western Europe, parts of Middle East.

Homo sapiens

Evolved in Africa, oldest fossils are 195-160,000 years old in Ethiopia. Lack heavy brow ridges, slender bodies, long limbs. The only extant hominin.

Recent Out of Africa (ROA) hypothesis

Proposes that modern humans originated in Africa and then spread throughout the rest of the world, replacing other human species. Supported by genetic and fossil evidence.

Δ32 deletion mutation of the CCR5 receptor gene

Confers pathogen resistance; originated 700-2000 ybp, highest in Europe/Middle East; possibly selected for during Black Death; also resists HIV.

Adaptive radiation

A small number of ancestral species increases to give a larger number of descendant species

Small scale extinction

Local and occur over a short period of time, loss of single or few species with limited distribution; can accumulate to cause complete extinction

Red Queen hypothesis

Extinction happens because environmental changes happen faster than the rate of adaptations

Mass extinction

Global or continental occur over long stretches of time. Loss of many species and even taxa

Big five mass extinctions

Late Ordovician (400 mya)

Late Devonian (350 mya)

End Permian (250 mya)

Late Triassic (210 mya)

End Cretaceous (80 mya)

Biggest extinction in history

End Permian, 80-96% of species were lost

Passive replacement

Taxa that evolve slowly to replace prior species (ex. mammals and dinosaurs)

Competitive replacement

Competing with prior species

Darwin’s 4 postulates

1. Individuals within a population are variable

2. Some variations are passed on to offspring

3. Some individuals are more successful at surviving and reproducing than others

4. The survival and reproduction of individuals are not random – individuals that survive and reproduce the most are those with the most favourable variations

‘Struggle for existence’ (Malthus)

Animal populations should outgrow limited resources very quickly. Individuals with advantageous variations would do better in the struggle for survival and thus would produce more offspring

Fitness

1. A measure of individual success in evolutionary terms

2. The average number of offspring produced by individuals with one genotype relative to the number produced by individuals with different genotypes

Systematics

Evolutionary relationships between species

The extended phenotype

A phenotype should not be limited to biological processes such as protein biosynthesis or tissue growth, but extended to include all effects that a gene has on its environment, inside or outside the body of the individual organism

Behavior

The sum of the responses of an organism to internal and external stimuli-can be either instinctive or learned

Tinbergen’s four questions

Niko Tinbergen won the Nobel prize in 1973 for his contributions to behavioral research; he developed four major questions to determine how behavior worked