Biology Module 3

define selection pressures

features that affect an organism’s ability to survive in its ecological niche

define abundance

how many members of species live throughout ecosystem

what causes abundance to increase/decrease?

• immigration/emigration of species

• influx/deflux of predators/prey

• change in structure

define extinct & give example

no longer present e.g. tasmanian tiger/thylacine

define extant & give example

still existing in high numbers e.g. cane toads

define extirpate & give example

no longer exist in specific area

define endangered & give an example

limited number in the wild e.g. tasmanian devil

what are the biotic selection pressures? give an example

• availability of mates to reproduce with

• survical of offspring

• number of competitors/prey/availability of food

• number of predators

• presence of disease

• e.g. coconut crab; limited food (selection pressure) drove evolution of long legs to allow crabs to climb coconut trees & strong claws to crack coconut

what is the impact of introduced species/pests on agriculture?

• invade farms with animals/crops

• eat grass needed for sheep & cattle

• compete with farmers’ crops for water, nutrients from soil & sunlight

what is the impact of introduced species/pests on native wildlife?

• compete for food & habitat, cause disease, predators of native wilflife

• reduce biodiversity of native species

what is the impact of introduced species/pests on soils?

• introduced plants & weeds have shallower roots, hence do not protect soil as much from rain & wind & cause soil erosion/land degradation

what is population density/size determined by?

• birth (fatality)

• immigration

• emigration

• death (mortality)

• geographic distribution

• population explosions (growing exponentially over long periods)

what are the types of geographic distribution? (identify & draw)

what are the abiotic selection pressures?

• topography: shape of land, affects water runoff & soil type, create microclimates

• aspect: direction a slope faces; causes variatio in amount of sunlight received by an area of land

• altitude: height of land mass above sea leve, increased altitude = air pressure/oxygen/temperature decrease

• organism tolerance: ability to survive within physical conditions of environment, every organism has a tolerance range (range of conditions it can survive)

why were cane toads introduced?

introduced to Queensland from Hawaii to biologically control cane beetle in sugarcane plantations

was the introduction of cane beetles successful?

failure; beetles lived too high up on canes, cane toads rapidly reproduce & eat anything → became invasive

what were the selection pressures & evolution caused by cane toads?

• spatial sorting: toads at “invasion front” evolved to have longer, stronger legs & directional movement, allowing travel of 50-60km per year

• physiological impact: rapid movement → older, faster toads more prone to spinal arthritis

• impact on native predators: cane toads secrete toxic bufotoxin (severe selection pressure for native predators e.g. red-bellied black snakes)

  • predators that eat toads die → snakes evolved to develop smaller heads to prevent swallowing adult toads

why was the prickly pear introduced to Australia?

introduced to Australia from South America for cochineal dye industry & as livestock food source

why did prickly pears become invasive?

lcked natural selection pressures (e.g. native predators, specific diseases) → spread rapidly, covering 25 million ha of agricultural land

what were the positive/negative selection pressures & evolution caused by prickly pears?

• positive: arid Aus climate & fertile soils allowed prickly pear to outcompete native flora

• negative: scientists introduced Cactoblastis cactorum (moth) from SA as biological control agent

  • moth larvaes fed inside cactus pads → plant died & collapsed

  • quickly reduced prickly pear distribution by 99%

what are structural adaptations? give examples

modification of species structures that give organism advantage in particular environment

• SA:V e.g. ears of elephant as cooling mechanism during hot temperatures

• body coverings e.g. fur, feather for warmth/heat

• dentition e.g. K9’s sharp teeth, herbivores have flat top teeth

• vascular body parts e.g. plants with large channels for water transport

what are physiological adaptations? give examples

affect functioning at different levels of organisation, including:

• biochemical reactions in organelles e.g. photosynthesis, respiration

• camouflage e.g. camels metabolise fat-storing humps to produce metabolised water

• evaporating cooling e.g. sweating; moisture evaporates from skin & draws away body heat

• countercurrent heat exchange e.g. penguins; warm blood leaves bird’s body core & travels down leg through arteries

• torpor

• CAM photosynthesis

• frost tolerance

• regulation of salinity

what are behavioural adaptations? give examples

actions that an organism takes to improve survival/reproduction

• seeking/leaving shade/shelter

• huddling

• migration

• tropism

• nastic movement

  • non-directional responses to stimuli

  • associated with plants

  • movement due to changes in turgor or growth

  • e.g. decrease in turgor pressure causes shrinkage, increase brings swelling

construct a flow chart of the finches of the Galapagos islands

mainland finches (common ancestor) → selection pressure (e.g. food, temp) → migration to nearby islands → adapt to selection pressure on those islands → speciation (new species)

define natural selection/survival of the fittest

process by which organisms best suited to environment survive & reproduce, passing on favourable traits

what are the 5 characteristics of natural selection?

• Organisms produce more offspring than can survive

• Variation occurs amongst species

• Variations are passed onto offspring

• Some variations help individuals survive

• Over time, favourable traits cause population change

what is the process of natural selection?

1. Variation between individuals in any given species

2. When faced with selection pressure, not all individuals in a species live to reproduce

3. Individuals with less favourable variations die, while those with favourable traits survive

4. Those who survive reproduce & pass favourable traits onto offspring

what are the types of biodiversity & define species evenness? give examples

• Genetic: total number of genetic characteristics in genetic make-up of species e.g. human eye & hair colour

  • Gives robustness to survive changing conditions

  • Safeguards against new pests & environmental change

  • wild species of crops contain a large natural gene pool

  • Should be maintained for genetic diversity of future & future breeding

  • Decrease in genetic diversity lead to lack of genetic vigour or strength

• Species: measure of diversity of different species in ecological community e.g. coral reef (thousands of species of fish, turtles, etc.)

• Species evenness

  • If number of individuals within a species if fairly constant across communities then it is said to have high evenness

  • High evenness leads to greater diversity

• Ecological: variation of different ecosystems found in region

  e.g. Great Barrier Reef (shallow coral reefs, seagrass meadows, mangrove forests)

  • Many ecosystems that are resistant to human impact show high level of biodiversity

define adaptive radiation

process in which organisms diversify rapidly from ancestral species into multitude of new forms, particularly when change in environment makes new resources available, alters biotic interactions, opens new environmental niche

what is the order of evolution?

1. Organic molecules - methane

2. First membranes

3. Prokaryotic autotrophic cells - bacteria & archaea

4. First eukaryotes

5. First multicellular organisms

6. Colonial organisms

define & describe microevolution

• Microevolution: describes changes that take place over period of time

  • Does not result in speciation

  • Changes lead to change in population due to changes in frequency of alleles found in that population

  • Gene may have multiple alleles (e.g. blood alleles: A, B, O)

define & describe macroevolution

• Macroevolution: result of numerous changes due to microevolution

  • Result in speciation

  • Very slow process

  • E.g. development of Homo sapiens took place over millions of years

what are the forces that change population & allele frequencies (for both evolution types)? define & give examples

• Mutations: changes in genetic code, leads to variation

• Gene flow: exchange  of alleles between populations

  • When new population migrates & joins another population, leads to change in frequency of alleles in population

  • E.g. bees transferring pollen from one flower to another

• Genetic drift: change in allele frequencies in population as a result of chance

  • When alleles naturally change through generation

  • Occurs in small populations

  • Main triggers: founder & bottleneck effect

• Founder effect: small population is isolated & forms new population

  • E.g. species can’t cross river, forms new species

• Genetic bottleneck: large population dramatically reduced in size, therefore reducing genetic variation

  • E.g. going through sudden loss of food source

define speciation

development of new species from pre-existing species

define allopatric, allo & patric

• Allopatric: when population becomes divided by geographical barrier, resulting in reproductive isolation

  • Allo = different

  • Patric = homeland

define peripatric & peri

• Peripatric: small population becomes isolated at edge of range of parent population

  • Peri = around

define sympatric & sym

• Sympatric: populations become divided so that gene flow is interrupted between 2 groups, populations inhabit different microhabits within larger geographical area

  • Sym = together

define parapatric & para

• Parapatric: gene flow is reduced/halted due to factors that result in population occupying different niche

  • Para = beside

evolution of horse: cause, ancestor, selection pressure, advantages

• Result of accumulating microevolutionary changes & thus speciation

• Ancestral horse lived 52 million years ago & was only 10kg

• Selection pressure: grasslands gradually overtaking forests & side toes shrinking → horses increased in weight → reduction to middle toe

• Advantages of one toe:

  • High-speed running & dodging sideways

  • Jumping

  • Covering 100 miles a day (if properly trained)

what do playtpuses show similar features to?

birds, reptiles & mammals; webbed feet, venom gland, hair on body

what does genetic evidence suggest

suggests that monotremes split off first evolved

what was the first split between

marsupials & mammals

how do platypuses reproduce?

lay egg with yolk

how do platypuses hunt?

locate prey with eyes closed by sensing electric pulses given off by muscles

what kind of evolution is the platypus?

macroevolution

convergent evolution: define, give an example, reason for similarity

• Convergent evolution: process by which two not closely related species become more phenotypically similar due to environmental pressures that are similar

• Evolution occurs through natural selection of similar features in unrelated organisms

• E.g. dolphins (mammals) & sharks (fish) have streamlined bodies ti boost speed when swimming

• Reason for similarity: sharing similar niche in environment

divergent evolution: define, give an example, reason for similarity

• Divergent evolution: process of two or more related species becoming less similar

• Separated populations diverge, whether by random factors e.g. genetic drift or natural selection

• E.g. ancestral finishes arrive on Galapagos islands & evolved into different species of finches with different beaks, diets, ecological niches

• Reason for similarity: relatively common ancestor

what does punctuated equilibrium suggest?

suggests that over geological time, main selective pressure for a species will be stable, yet evolution has rapid movements where transitional forms aren’t preserved (i.e. does not follow pattern; rapid movement then no change then change again)

explain Darwin’s description of evolution

Darwin described evolution as gradual change over time

• If true, then fossil record would show gradual change in species over time with many intermediate fossils (must be remembered: fossilisation is rare)

• Intermediate fossils would demonstrate that microevolutionary steps gradually accumulated leading to speciation

  • However, fossil record often does not show this with there being large gaps

  • Rarity of process may have led to gaps

• 1972, theory of Punctuated equilibrium proposed by Stephen Jay Gould & Niles Eldredge to explain what was seen in fossil record

  • Suggested that gaps did represent time with no evolutionary change (times in which populations were stable)

  • Periods of stability punctuated by rapid evolutionary changes in response to environmental change

what is the evidence that supports Darwin & Wallace’s Theory of Evolution by Natural Selection?

• biochemistry

• comparative anatomy

• analogous structures

• vestigial structures

• biogeography

• transition fossils

• DNA hybridisation

how does biochemistry support Darin & Wallace’s Theory of Evolution by Natural Selection? give examples

• Genes tell which amino acids needed to build proteins needed

• Mutations over time alter amino acids that are the building blocks for these proteins

• The more similar the amino acids, the more recently they had a common ancestor

• Biochemical evidence: analysis & comparison at molecular level (e.g. humans & chimpanzees)

how does comparative anatomy support Darin & Wallace’s Theory of Evolution by Natural Selection? give examples

• Comparative anatomy (divergent evolution): comparison of anatomical features (e.g. cat & human)

  • Homologous structures: those similar in related organisms because they were inherited from common ancestor 

  • Although they have same basic structure, they lack same function in descendants

  • Five part limbs (pentadactyl limbs) of vertebrates considered to be similar structures

  • Diagram indicates they have common ancestor & underwent divergent evolution

how do analogous structures support Darin & Wallace’s Theory of Evolution by Natural Selection? give examples

• Analogous structures (convergent evolution): feature that evolved in two unrelated organisms for the same purpose

  • Still evidence for evolution because they show an accumulation of adaptations over time

  • Do not come from a common ancestor

  • E.g. human eyes & octopus eyes

define vestigial structures & give examples

structures that functioned in ancestral organisms but have no function in present-day organisms (e.g. human tailbone & appendix)

how does comparative embryology support Darin & Wallace’s Theory of Evolution by Natural Selection? give examples

• Comparative embryology (divergent evolution): comparison of embryos (e.g. humans & fish)

  • During embryonic development, all terrestrial animals have non-functional gill slits (reflection of aquatic common ancestor) & most have tails at some stage of development

how does biogeography support Darin & Wallace’s Theory of Evolution by Natural Selection? give examples + the major biogeographical zones

• Finding closely related species in same region rather than randomly placed around the world suggests evolution from common ancestor

• Some exceptions to this (above dot point) because of continental drift

  • E.g. large flightless birds only found in continents in the Southern Hemisphere (Africa: ostrich, PNG: cassowary, Australia: emu)

• World is divided into 6 major biogeographical zones 

  • Boundaries drawn according to distribution of vertebrate groups

  • Regions are based on the relationships of birds

how do transition fossils support Darin & Wallace’s Theory of Evolution by Natural Selection? give examples

• Show there are intermediate forms of distinct branches e.g. archaeopteryx has bird features (tail, teeth in beak, wings) and dinosaur features (beak, long neck, warm blood?)

• Fossils

  • Show progression of evolution from simple to complex organisms

  • Helps determine lineages of now extinct organism by examining fossils & comparing them to other extinct & modern species

how does DNA hybridisation support Darin & Wallace’s Theory of Evolution by Natural Selection?

• Separate strands of DNA from two species & mix together

  • More binding to form double strands = closer relationship

what are the techniques used to date fossils & the evidence produced?

• relative age

• absolute dating

• radiometric dating

• relative dating

• index fossils

describe the technique relative age dating & give an example

• If fossil is lower in rock strata than another fossil then the fossil is older

• Gives evidence of life that has become extinct (e.g. trilobites)

describe the technique absolute dating & give an example

• Determines how long ago a fossilised organism lived by studying radioactive elements

• E.g. carbon 14 used

  • Knowledge of how long it takes for carbon-14 to decay to a lighter form determines the percentage of it remained in the fossil, thus determining age

• Igneous layers (e.g. volcanic ash) are good to help with ageing layers of strata

describe the technique relative dating

• Compares age of one fossil or rock with another to determine which is older

• Relies on two basic facts:

  • Sedimentary rocks form strata (first & oldest stratum is found at bottom, younger & newer sediments then settles on top)

  • Fossils are the same age as the rocks they are found in

• Sometimes lowest strata is not the oldest; rock layers may fold over each other & can be turned upside down by earth movements

define & describe the technique index fossils

Index fossils: fossils that can be used to compare the ages of strata in different locations

• Comparing layers like this is called stratigraphy

• To be used as an index fossil, species must:

  • Have been fairly widespread in where it lived

  • Have lived in a fairly narrow period of time

  • Have been abundant

  • Be easy to identify

what kinds of cane toads reproduced more & what did that lead to?

Faster & larger cane toads reproduced more → whole population is slowly getting faster

why will cane toads continue to reproduce?

No selection pressures on cane toads → will continue to reproduce at exponential rates

explain the modern-day example of evolution: non-resistant bacteria

Non-resistant bacteria exist → bacteria multiply by the millions (some will mutate) → some mutations make the bacterium drug resistant (in the presence of drugs, only drug resistant bacteria survive) → drug resistant bacteria multiply & thrive