Ecology& Study of complex interactions referred to by Darwin as the conditions of the struggle for existence& Study of how organisms interact with each other and their environment

& Living things cannot exist alone – there must be a relationship between them& Living things are adapted to the environment where they live Abiotic factors (Non-living) Biotic factors (Living organisms) Soil Prey Climatic Predators Topographical Parasites/competitors Temperature Land: Wind speed, humidity, light intensity Water: Salinity, oxygen (dissolved), pH, exposure

Habitat: Physical location in which an organism lives

Levels of Ecological Organisation& Individual

& No 2 species can occupy the same niche (position a species occupies within its habitat, including physical space, interactions with other organisms and effects on environment)

& Population& Individuals of same species occupying a certain area = population

& Community& Different populations in an area which interact with each other = community& Living + Non-living

& Ecosystem & Consists of different species of a community, and their non-living environment & 4 basic elements: Abiotic component, biotic component, energy, nutrients

& Biome& Ecosystem is part of a biome

& Biosphere& All life is restricted to a zone called the biosphere – the region of earth’s land, water and air in which

organisms are found

Recycling of NutrientsNitrogen Cycle & Though atmosphere contains 79% nitrogen, only a few micro-

organisms can tap this source & Bacteria can fix atmospheric nitrogen, while others convert

ammonia to nitrate, making it available for incorporation into plant and animal tissues

& Lightning discharges also cause oxidation of nitrogen gas to nitrate, which ends up in soil

& Denitrifying bacteria reverse this activity and return fixed nitrogen to the atmosphere

& Nitrogen Fixation in Root Nodules& Root symbiosis between a higher plant and a bacterium& Bacteria fix atmospheric nitrogen& Important to nutrition of many plants (including legumes) & Provide plants with its nitrogen requirements& In return, they have access to a rich supply of

carbohydrates & Fixation of atmospheric nitrogen to ammonia occurs within the nodule, using the enzyme nitrogenase

& Human Intervention in Nitrogen Cycle & Haber process: ammonia and hydrogen gas are combined to form gaseous ammonia & Converted to ammonium salts and sold as inorganic fertilizers & Overuse of nitrogen fertilizers may lead to pollution of water supplies (especially if land clearance

increases the amount of leaching and runoff into ground and surface waters) & Use of anaerobic bacteria to break down livestock wastes, releasing ammonia into soil & Nitrogen is removed from land through burning, releasing nitrogen oxides into atmosphere& Lost by mining, harvesting crops and irrigation, which leaches nitrate ions from soil & Discharge of effluent into waterways

Carbon Cycle & Between living (biotic) and non-

living (abiotic) environment & Fixed in process of photosynthesis,

returned to environment in respiration

& Human activity has disturbed the balance of the carbon cycle through activities such as combustion (burning wood, fossil fuels) and deforestation

Water Cycle& Collects, purifies and distributes the earth’s fixed supply of water

Food Chains & Webs& Elements which make up living organisms are recycled& Except for energy, which flows from organism to organism and is finally lost to the atmosphere as heat

Organism Name Consumer Trophic LevelGrass Producer Producer 1st Insect Herbivore Primary 2nd Sparrow Small carnivore Secondary 3rd Snake Large carnivore Tertiary 4th

Food chains & Consists of a series of organisms through which energy is transferred& Each organism in the series feeds on and derives its nutrients/energy from the preceding one

P roducer & Autotrophs: Able to synthesize complex organic substances from simple inorganic substances & Make food from carbon dioxide, sunlight = energy source & Eg Plants, algae, some bacteria

P rimary Consumer & Heterotrophs: Unable to synthesize complex organic substances from simple inorganic substances& Feed on complex organic substances made by producers& Feed on producer: Herbivore/Omnivore

S econdary Consumer & Feed on primary consumer: Carnivore/Omnivore

T ertiary Consumer & Feed on secondary consumer: Carnivore/Omnivore

D ecomposers & Act on dead organisms& Break down organic matter into simple inorganic substances & Make nutrients available to the producers (recycles nutrients)& Eg Bacteria, fungi& Not part of the food chain (not “predators”)

D etritivore & Animals that feed on dead decaying matter (detritus) & Dead decaying matter passes through a detritivore, partly digested and absorbed, remains comes out in faeces & Eg Woodlice, maggots, sea cucumbers, earthworms

& Different from decomposers: they are larger in size, digest food internally

Trophic Level: one stage in a food chain & Food chains usually have less than 5 trophic levels & Inadequate energy in ecosystems to support more than 5 trophic levels & Only 1% of sun’s energy reaching the earth’s surface is trapped by producers& Only 10% of energy in each trophic level is transferred to the next level& The more levels there are in a food chain, the more unstable it becomes (vulnerable to changes in species and

populations)

Food Webs & Food chains interconnected in a criss-cross network of nutritional relationships& Single species may form part of many different food chains, occupying different trophic levels & Complexity of a food web makes it stable

Transfer of Energy between Trophic Levels & Only about 10% of energy in each trophic level is converted to biomass in the next trophic level & Transfer of energy from producers to primary consumers is the least efficient (1%-10%) of producer biomass

& Plants contain high levels of cellulose and lignin, which many animals are unable to digest & Leaves of some plants are poisonous and thus not consumed by animals& Certain parts of the plant are inaccessible & Some plants die before being eaten

& Transfer of energy from primary consumers to secondary consumers (10%-20%) & Bulk of energy lost to respiration& Lost to excretion/egestion& Lost to death& Certain parts of primary consumer are inedible& Some primary consumers are inaccessible to secondary consumers

& Possible things that can happen to energy taken in for each trophic level& Can be passed onto the biomass of the next trophic level in the food chain when the organisms is eaten& Can become stored in detritus (energy passed on to decomposers when detritus decays) & Can be converted to heat energy by inefficient chemical reactions, radiated by warm bodies, or in friction

due to movement. Heat energy lost to surroundings, cannot be regained by living organisms & Energy losses in an ecosystem

& Only 10% of energy available in food is incorporated into biomass& Remaining 90% is lost as

& Faeces& Used in respiration, lost as heat& Used to increase biomass of herbivore (energy of production = 10%) & Lost in urine

Ecological Pyramids

& Quantify feeding relationships in a community to enable us to compare the different ecosystems and assess the potential of an ecosystem for the production of food

& Producers always at the bottom

Pyramid of Numbers& Indicates number of organisms for each species at each trophic level in a unit area at a given time & As pyramid ascends, the number of organisms decreases but the size of each organism increases & Limitations:

& May be inverted (does not show how an ecosystem works, eg there may be only 1 tree but that has a lot of energy/biomass)

& Difficult to represent an entire community using the same scale as the number for each species may vary widely

& Does not account for immature forms of species& Amount of biomass/energy available to next trophic level is not known

Pyramid of Biomass& Represents the total biomass of organisms of each species at each trophic level in unit area at a given time & Meaningful comparisons of different trophic levels are possible & Procedure

& Estimate no. of individuals of each species & Determine average dry mass of individuals (because water content varies) & Total biomass = no. of individuals X average dry mass

& Limitations& Determination of biomass is destructive, affects actual food chain/web& Usually only a small sample of individuals in a population is taken to measure for biomass, thus it may not

be representative

Pyramid of Energy& Represents flow of energy through each trophic level in unit area in an interval of time (usually 1 year) & Usually similar to biomass (energy generally comparable to biomass) & Advantages

& Takes into account productivity of species (amount of energy produced by a species) & An upright pyramid is always obtained (shows how an ecosystem works) & Takes into account that different chemicals and species may not have the same energy content per unit

mass& Limitations

& Determination of biomass is destructive, affects actual food chain/web& Usually only a small sample of individuals in a population is taken to measure for biomass, thus it may not

be representative & Time interval usually quite long (1 year) & Difficult to measure energy due to problem of heat loss

Relationships between OrganismsPredator-Prey

& 1 species kills and feeds on another & Predator population < Prey Population& Important relationship to regulate and maintain stability in the ecosystem & Prey needs the predator just as much as predator needs prey& Eg Me and gummy bears

Symbiotic & M utualism

& Association between 2 species that is beneficial to both& Eg Fungus and Alga (cynobacteria) – gives rise to lichens & Eg Termites have a mutualistic relationship with cellulose-digesting bacteria in their guts

& P arasitism & Exploitation relationship in plants and animals& Parasite exploits resources of its host (eg food, shelter, warmth, protection) to its own benefit& Host is harmed but not killed & Endoparasites

& Highly specialized to live inside their hosts, attached by hooks/suckers to host’s tissues& Eg liver fluke, tapeworms, nematodes

& Ectoparasites & Live attached to the outside of the host, where they suck body fluids, cause irritation or act

as vectors for disease-causing micro-organisms& Eg ticks, mites, fleas & Eg Flea sucks dog’s blood (for nutrition) and the dog suffers (from potential disease that the

flea may bring, or from lack of blood) & C ommensalism

& 2 species form an association where 1 organism (commensal) benefits, and the other is neither harmed or helped (1 benefit, 1 not affected)

& Eg Grouper and remora & Eg Anemone shrimp and sea anemone (shrimp is protected from predators by anemone’s tentacles)& Eg Bird lives in a tree (benefits from having shelter), tree is not affected

Inter/Intra-specific Competition& Compete for resources (eg food, water, land territories, nesting sites, nutrients, light)& Competition for same food resources are dominated by largest and most aggressive species & I nterspecific usually less tense than intraspecific (same species) & Niche Differentiation: Coexisting species have evolved slight differences in their realized niches, even though

their fundamental niches may overlap & Every ecosystem has a carrying capacity (number of individuals in a population that the environment can

support). population = competition, so when the demand for a particular resource exceeds supply, that resource becomes a limiting factor

&& Gause’s Competitive Exclusion Principle

& Two species’ resource use curves will overlap – intense competition & Eg Storks, vultures and hyenas compete for carcasses

Strategies/Defence MechanismsPrey-capturing Strategies: Predators have numerous adaptations for locating, identifying and subduing prey& Concealment (camouflage)

& Strike only when prey is within reach& Filter feeding

& Filter water to extract tiny organisms (eg marine animals filter water to find plankton) & Eg Barnacles, baleen whales, sponges, manta rays

& Tool use& Use natural resources found in habitats to make tools to capture prey& Eg Chimpanzees use carefully prepared twigs to extract termites from mounds

& Stealth& Night-hunting ability enhanced by infrared senses& Eg some poisonous snakes

& Lures& Use lures to attract prey within striking range& Eg Angler fish, glow worms, spiders

& Traps& Capture prey so they can’t escape& Eg Spiders use strong silk sticky threads to weave webs

Predator Avoidance Defences & Mimicry

& Mimic harmful attacks to scare off the predator & Eg Wasp beetle

& Poisonous& Animals advertise and broadcast that they are unpalatable & Have brightly coloured and gaudy markings & Eg Monarch butterfly

& Visual deceptions& Deceptive markings (eg fake eyes) can deceive predators, giving prey time to escape & Eg Owl butterfly

& Chemical defence& Offensive smelling chemicals& Eg American skunks squirt nauseous fluid at attackers

& Offensive weapons& Vital to actively fend off attack by predator& Eg Deer antlers

& Camouflage & Cryptic shape and colouration allows animals to blend into background & Eg Leaf insect

ClassificationKingdom – Prokaryote, Plantae, Animalia, Protista, FungiPhylum

ClassOrderFamilyGenusSpecies

Distribution of life on earthP rerequisites for life & Climate& Oxygen, water, food& Temperature, rainfall& Sunlight& Substrate

& Mostly found in tropics, near water (along equator) & Competition for limited resources: there is a limit as to how much a population can grow

H ow is life distributed? & Temperature& Latitude (biomes are less diversified towards Poles) & Elevation (quality of air) & Soil& Fresh water

B iomes & Tropical rainforest – most diversity! (stable climatic conditions, high rainfall) & Deserts& Tundra& Savannah& Temperate forests& Corals

Practical C ensus & Count entire population& Only possible with very obvious individuals and ability to cover entire spread of population range (eg census of

dogs in a park)

S ampling & Count just part of the population, then extrapolate to estimate total population size& Must know how reliable samples are & Degree of errors involved when extrapolating depends a lot on variability across range of population & Use variables and factors to identify each organism’s role in environment and its niche& Compare with previous sample to observe any changes in population in relation to changes in environment

Direct counts & Relevé: for vegetation sampling& Quadrats: markers that isolate a sample area to count the population size of different species within the area& Capture techniques: for animals

I ndirect counts & Inferences! From& Evidence of animals’ presence (eg nests, droppings, animal tracks, recorded animal calls)& Evidence from human activities (eg fishing quotas, catch rates)

Methods of sampling Sessile species (don’t move around) Mobile species Quadrat samplingSampling a unit of known area (square frame) & Point quadrats

& Estimate percentage cover of species in an area

& Quadrats of different sizes & Percentage cover of species within a

community

Mark & Recapture & Animals must live normally even after being

marked& Marking cannot affect behavior and health& Cannot make organism more vulnerable to

predation & Cannot allow for trap-shyness or develop trap-

favouritism

Sampling designs& Regular/Uniform: samples taken in a regular pattern (eg a line)& Random: samples are taken from randomly chosen spots (eg numbers of grid coordinates)& Stratified random: random samples are allocated deliberately to each of the recognized different

environmental patches in the sample area

Method Equipment & Procedure Info & Considerations Point Sampling

& Area under study is divided into grid system of boxes

& Random numbers are chosen as coordinates for the grid box to place quadrat

Info & Determines species abundance and community

composition& If samples are large enough, population characteristics (eg

age structure, reproductive parameters) can be determined Considerations & Time efficient & Suitable for most organisms & Minimal environment disturbance & Species occurring in low abundance may be missed

Transect Sampling

Lines are drawn across a map, organisms occurring along the line are sampled

Info & Well-suited to determining changes in community

composition along an environmental gradient & When placed randomly, they provide quick measure of

species occurrence Line Transects& Tape/rope marks line& Species recorded at regular

intervals & Lines can be chosen randomly,

Considerations & Time-efficient & Most suitable for plants and immobile/easily caught

animals & Minimal environment disturbance

or may follow environmental gradient

& Species occurring in low abundance may be missed

Belt Transects& Measured strip located across

the study area to highlight any transitions

& Quadrats used to sample the plants and animals at regular intervals along the belt

& Plants and immobile animals are easily recorded

& Mobile or cryptic animals need to be trapped/recorded using appropriate methods

Considerations & Time-consuming to do well and thoroughly& Most suitable for plants and immobile/easily caught

animals & Good chance of recording most or all species& Efforts should be made to minimize disturbance to

environment

Quadrat Sampling

& Quadrats placed randomly or in a grid pattern on sample area

& Occurrence of organisms in these squares is noted

Info& Well suited to determining community composition and

features of population abundance & Species density, frequency of occurrence, percentage

cover, biomass (if harvested) Considerations & Time-consuming to do well& Most suitable for plants and immobile/easily caught

animals& Quadrat size must be appropriate for the organisms being

sampled and the information required& Disturbing if organisms are removed

Mark & Recapture

& Animals are captured, marked and released

& After a suitable time period, animals are re-sampled

& Number of marked animals recaptured in second sample is recorded as proportion of the total

Info & Determine total population density for highly mobile

species in a certain area (eg butterflies) & Movements of individuals in the population can be tracked

(esp when used with electronic tracking devices) Considerations& Time consuming to do well& Not suitable for immobile species & Population should have finite boundary& Period between samplings must allow for redistribution of

marked animals in population& Markings should cause little disturbance and should not

affect behavior

Quadrat Sampling & Used to find

& Population abundance (number)& Density& Frequency of occurrence& Distribution

& Density = total no. of individuals counted/(no. of quadrats x area of each quadrat)& Guidelines for use

& Area of each quadrat must be known exactly& Enough samples must be taken (to get representative results)

& Population of each quadrat must be known& Appropriate size for organisms/habitat& Representative of whole area

& How to carry out line transect sampling? 1. Stretch a string between 2 markers (either random, or follow environmental gradient)2. Mark off measured distance intervals on string3. Count no. of individuals of each species at each point

& How to get accurate results?& Move line& Repeat& Get average

Lincoln IndexTotal population = No. of animals in 1 st sample (all marked) x Total no. of animals in 2 nd sample

No. of marked animals in 2nd sample (recaptured)1. Population is sampled by capturing as many of the individuals as possible and practical2. Each animal is marked in a way to distinguish it from unmarked animals 3. Return animals to habitat, leave them for a long enough period for complete mixing with population4. Take another sample of the population (don’t need same sample size as 1st, but must be large enough) 5. Determine numbers of marked to unmarked animals in second sample6. Use Lincoln’s Index to calculate total population

L imitations & While capturing: may injure animal, or alter its behaviour pattern& Mark used may harm the animal (eg toxic paint) & Marks may make animals more/less attractive to predators & Method assumes that all animals in population are equally catchable (however it varies according to life

stages, seasons, times of day etc – must sample under similar conditions) & Trapping responses

& Trap-shy: avoid traps after first capture & Reduced by choosing a method that will not distress the animal unduly& Trap-happy: attracted to traps, especially if traps are baited & Reduced by setting out baited traps (without actually trapping) sometime before 1st sample is taken –

allow all animals to become equally trap-happy

Urban VegetationIncrease temperatures Decrease temperaturesReduce relative humidity values Increase relative humidity Cause creation of “heat islands” Modify human climatic comfort

Factors affecting abundance of biodiversity& Sunlight& Water& Climate

& Substrate& Non-seasonability

Mans Impact on the

EnvironmentTragedy of the Commons& Pasture shared by x herdsmen& Benefit of increasing 1 more to the flock = +1 to individual herdsman& Detrimental effects of overgrazing = (-1/x) shared by all who use the pasture& Thus the individual herdsmen will continue to increase sheep because the benefits for him is still positive,

though the negative effects on everyone else accumulates

& Same concept, apply to anything else& Commons = Resource available to ALL& Trees (deforestation)& Fish (overfishing) & In the end ALL THE COMMONS WILL RUN OUT ):

Overfishing & 9 out of 10 big predators have been removed in the past 50 years& 90% of world’s fish are gone

Sustainable development & Process of developing land, cities, businesses, communities that “meets the needs of the present without

compromising the ability of future generations to meet their own needs”& Sustainability: Consumption of resources must be equal/less than nature’s ability to replenish itself

Solutions& Set fishing quota

& Eg Blue fin tuna can sustain an annual catch of 15,000 tons (total catch by 43 countries in 2006 – 553,000 tons)

& Limit use of harmful technology& Aquaculture

& Food security: food easily available without need of technology (immediate supply of food – no need destroy natural stock)

& Vulnerable to disease: 1 infected, all infected& No circulation of water (high nitrogen content – bad)

& Education: switching consumers’ diets & Impose minimum size caught (ensure young tuna mature into adults for continued reproduction

Air pollution

Global Warming Causes

& Greenhouse gases trap infrared radiation (heat) close to the Earth’s surface & Solar radiation can enter lower atmosphere but cannot escape & Aggravated by increased greenhouse gases:& Carbon dioxide released by combustion of fossil fuels & Methan produced in the guts of ruminants, and in waterlogged conditions of swamps and rice fields& CFCs (chlorofluorocarbons) from aerosol propellants and refrigerator coolants

Effects & Greater climactic extremes – strong winds, heavier rainfall, unseasonal weather& Melting of polar ice and changes in density of sea water – raising sea levels and flooding & Evaporation of water from fertile areas – deserts form& Pests may spread to new areas& All of above may cause loss of crops& But higher temps and more carbon dioxide may mean more photosynthesis, and more food production

Solutions& Reduce burning of fossil fuels – explore alternative energy sources& Reduce cutting of forests for cattle ranching or rice growing& Replant forests

Acid RainCauses

& Human activities release acidic gases& Sulphur and nitrogen in fossil fuels are converted to oxides during combustion& More oxidation occurs in the clouds, oxidation is catalysed by ozone and by unburnt hydrocarbon fuels & Oxides dissolve in water, and falls as acid rain

Effects & Soils become acidic – leaching of minerals, inhibition of decomposition& Water in lakes and rivers collect excess minerals – causes death of fish and invertebrates so that food

chains are disrupted& Forest trees suffer starvation because of leaching of ions and destruction of photosynthetic tissue

Solutions& Clean up emissions from power stations with scrubbers& Clean up emissions from car exhausts with catalytic converters

L ead Causes

& Lead compounds are added to petrol to prevent “knocking” (inefficient burning of the petrol-air mixture)& Released into atmosphere from exhaust gases

Effects& Lead compounds absorbed into the body through inhaled air may:& Slow down mental development& Damage the liver

Solutions& Reduce use of “leaded” petrol

S moke Causes

& Inefficient and incomplete combustion of fossil fuels & Eg bonfires, or clearing stubble from fields

Effects& Less light can penetrate atmosphere& Smoke deposits cover leaves & Reduced photosynthesis, reduced crop yield & Particles in smoke also irritate eyes, nose, lungs & Some smoke (eg from burning plastic) can also be poisonous

Solutions& More efficient burning, in well-designed furnaces& Burning “smokeless” fuels

Water PollutionFertilisers and Sewage – Eutrophication Causes

& Fertilizers& Nitrates and phosphates are added to soil by farmers& Washed into water by rain – Leaching

& Sewage& Organic food for bacteria& Contains phosphates from detergents

& Liquid manure (slurry) washed out of farmyards & Water that contains few nutrients is rich in oxygen and supports a wide variety of living organisms& Oxygen enters water from atmosphere by diffusion and from photosynthesizing aquatic plants& Simpler forms of life (algae, bacteria) are controlled because low concentration of nutrients such as

nitrate is a limiting factor for their growth& More nutrients available

Effects & Algae and other surface plants grow very rapidly, block out light to other plants & Rooted plants die, their bodies provide more nutrients& Bacteria population increases rapidly & As they multiply, bacteria consume oxygen for aerobic respiration& Biological oxygen demand in water (depleted oxygen levels) & Other living creatures cannot obtain enough oxygen, so they die & High nitrate levels can be dangerous to human babies

Solutions & Do not allow excess nutrients into the water& Treat sewage before it enters rivers& Prevent farmyard drainage entering rivers and ponds& Control use of fertilizers

& Apply only when crops are growing& Never apply to bare fields& Do not apply when rain is forecast

& Do not dispose of waste fertilizer into rivers and ponds& Bubble a stream of air through badly polluted ponds

Oil PollutionCauses

& Oil tankers spill their contents, by accident or deliberately (during cleaning of storage tanks) & Occasional damage to pipelines at oil terminals

Effects& Most of oil floats on surface of water, causing

& Deaths of sea birds since feathers cannot insulate when coated with oil& Fish directly poisoned& Marine mammals killed by eating poisoned food or loss of fur’s insulating capacity

& Oil is also washed onto beaches, causing& Deaths of organisms such as limpets, periwinkles and seaweeds& Loss of income from tourism

Solutions& Strict control of oil handling& Severe fines for breaking the rules concerning oil handling& Bioremediation – using living organisms to clear up pollution (eg some bacteria can consume oil if fed with

a source of sugar) & Volunteers can wash sea birds and mammals to remove oil

T hermal Pollution Causes

& Water used as coolant in power stations and industries& Water cools processes but is itself warmed up& Hot water discharged into rivers/seas

Effects& Temperature of river raised& Lowers oxygen concentration of water because solubility of oxygen in water falls as temp rises& Causes fish, invertebrates and bacteria to become more active, so they respire more and consume even

more oxygen& Allows colonization by foreign species, which may affect food chains

Solutions& Control output of hot water so that it is rapidly cooled by river/sea& Do not allow discharge of hot water into still/slow-moving rivers/canals

Metals Causes

& Lead enters water because& It dissolves from lead pipes (plumbing)& Lead weights are discarded by anglers

Effects& Lead compounds are toxic, and accumulate via aquatic food chains

Solutions & Replacement of lead pipes used in plumbing

& Strict control of angling – use of alternatives to lead weights& Planting of reeds around ponds and lakes – remove many toxic compounds from water without

themselves being affected

P esticides Causes

& Over use of pesticides on agricultural land can raise pesticide levels in water & Amplified as they pass through food chains

Effects& High concentrations of pesticides accumulate in tissues of top carnivores & May be toxic – affect its metabolism, etc

Solutions& Use degradable pesticide& Explore alternative methods, eg biological pest control& Crops that are GM may reduce need to use insecticides

Bioaccumulation& Higher-order consumers ingest toxic levels of a chemical because they eat a larger number of lower-order

consumers& Beluga whales example:

& How toxic materials accumulate at highest trophic level& Come up with questions and hypotheses

Evolution& Process that results in heritable changes in a population spread over many generations & Biological evolution is change in properties of populations of organisms that transcend the lifetime of a single

individual & Any change in frequency of alleles within a gene pool from one generation to the next

Theories of EvolutionLamarck’s TheoryGiraffes! & As trees grew taller in the African savannah, leaves and fruits became out of reach& Giraffes stretched their necks to reach for leaves, and this active use of necks resulted in the enlargement and

lengthening of necks & Giraffes passed on these acquired genes to the next generation, which continued to “grow” their necks & Ultimately resulted in giraffes with long necks

Theory& Hypothesis of The Inheritance of Acquired Characteristics & A changing environment creates a need for certain features to be developed in order to survive& Acquired Characteristics: Through use or non/use, those features needed for survival are developed in each

individual& Inheritance: Beneficial characteristics are somehow passed on to their offspring, who can continue that

development& New species: Eventually, over many generations, enough differences have developed that we can say there is

a new species

Darwin’s TheoryFinches! & Noticed 13 different species of finches within the different islands of the Galapagos& Appeared to be related to the only finch found on the mainland of South America& Finches all had different beaks that appeared to have different functions& An ancestral stock had migrated to the islands where they underwent profound changes under the different

conditions of the individual islands & Single ancestral group could give rise to several different varieties or species

Observations& Populations have potential to increase exponentially& Populations are fairly constant in size& Natural resources are limited & There is variation within a species, and variation is inheritedDeductions

& There is a struggle for existence among individuals in a population – only some survive& Individuals with favourable variations are more likely to survive and reproduce& Accumulation of variation over many generations is evolution

Adaptive Radiation& Single species develops into a wider range of advanced forms, which is adapted to particular environmental

conditions& Different size and shape of finches’ beaks so that they can feed on available food & Better survival advantage if they are better at eating local food

Theory of Natural Selection 1. Overproduction of Offspring

& All individuals of a population are capable of reproducing large numbers of offspring & If all offspring survived, there would be increase in size of population

2. Constancy of Numbers & Although organisms are capable of producing large numbers of offspring, most populations remain

relatively constant in numbers & Because most offspring die before they reach reproductive age

3. Variations within a Population & Individuals of a population differ from each other & Variations are a pre-requisite for evolution by natural selection & Variations arise spontaneously before a change in the environment & Not formed as a result of the new environment to make individuals better adapted& Environment does not determine what structures an individual should develop during its lifetime & Environment only selects those individuals who by chance happen to be better adapted

4. Change in Environment & Changes in climate, topography, food supply, predators, etc

5. Struggle for Survival & Because of overproduction of offspring and constancy of numbers, individuals are constantly competing

with each other for the limited resources (eg food, shelter) & In the struggle for survival, only a few individuals reach maturity and reproduce

6. Survival of the Fittest & “Fitness” = ability of individuals to survive to produce viable offspring& Within the population, some individuals are more adapted to the existing environmental conditions than

others& Some are better adapted to survive till maturity and produce viable offspring& These individuals are selected by environment of nature

7. Like produces Like & Individuals who can survive to maturity are likely to produce offspring similar to themselves & The beneficial characteristic which gave them an edge over others is likely to be passed onto the offspring

8. Formation of a New Species & Individuals possessing an advantageous characteristic have a greater chance to survive to maturity and

reproduce, as compared to those without that characteristic& Over generations, the proportion of individuals with the trait increases& The inheritance of 1 trait may lead to formation of a new strain, but not a new species

& Formation of a new species: Only after the development of several characteristics in a particular direction over many generations

& Natural selection that occurs over a long period of time results in evolution& As long as the environment changes, a population will continue to evolve (Eg Changes in predators, climate,

natural resources for life) & Evolution may result in the organisms changing to a new species

Summary of Natural Selection Theory1. Overproduction: More offspring produced will ultimately survive and reproduce 2. Variation: Inheritable features vary for each individual 3. Change in Environment: Climate, topography, food supply, predators 4. Struggle for Existence: Mainly competition within species, for food, habitat, survival 5. Survival of the Fittest: More adaptive traits tend to survive longest and produce most offspring6. Inheritance of “Selected” Features: Traits involved are already inheritable, but may involve new combis7. New species, better adapted to environment: When collective traits of population differ significantly from

earlier population and can no longer reproduce with earlier population

Assumptions (needed for Natural Selection) & Traits seen must be found in genes and hence must be able to be passed on to the next generation& Traits arose from random events like meiosis and mutation and not by intent (not directed)

Differences between Lamarck and Darwin’s Theories & Lamarckian theory was incorrect! & Traits acquired by overuse of an organ can be transferred to next generation& Traits can arise due to intent, with organisms seemingly able to “will” their organs to grow or develop

Lamarck DarwinEnvironment changes, thus creating “need” to change Variations of inheritable features already normally existDevelopment of new features “in order to survive” Environment “screens out” features contributing to

survival, and tends to eliminate others Newly acquired traits somehow gets passed down to offspring

Those who traits that help survival tend to survive and have offspring, who inherit those traits

New species eventually New species eventually Based on ACTIVE RESPONSE TO CHANGE Based on PASSIVE PROCESSES (like random variation)

Take note! & Only groups can evolve (populations/species), not individuals) & Adaptations can only develop as characteristics of a species& Over a long period of time, involving many generations & Must not be confused with “adjustments” that individuals might make, consciously or otherwise, enabling it to

survive better (such as “developing resistance to a disease” or “adapting to higher altitude”)

Theory of Natural Selection

Neo-Darwinism& Incorporates the principles of Mendelian genes and knowledge of molecular biology

1. Populations have great reproductive potential but the number of individuals remain relatively constant& Many fail to survive& Checked by environmental factors & Competition for resources & Predation

2. Variations within a population arise as a result of spontaneous mutation& Not in response to the needs of individuals & Genetic variation arises from gene mutations, chromosomal mutations, meiosis, random fusion of

gametes 3. Individuals with genetic variations that are best suited to new environment are more likely to survive till

maturity and reproduce 4. Environment selects pre-existing forms that have selective advantage 5. Proportion of individuals at selective advantage increases 6. Lead to change in allele frequencies and over a long period of time, evolutionary changes and formation of

new species

Causes of Genetic Variation

G ene Mutation & Change in structure of DNA, occurring at a single locus on a chromosome & Result in formation of new alleles

& Processes/mechanisms: & Deletion: one or more nucleotides are moved from a sequence of nucleotides & Insertion: one or several nucleotides added to sequence of nucleotides & Substitution: a nucleotide is replaced by another & Inversion: when sequence of nucleotides becomes separated from the allele; rejoins at original

position but is inverted (reverse sequence) & New alleles increase gene pool for natural selection & Eg Sickle cell anaemia (substitution)

C hromosomal mutation & Change in structure of chromosome (involving gene loci) or change in number of chromosomes & Mechanisms:

& Deletion: 2 points of chromosome breaks, middle part falls out & Inversion: 2 points of chromosome breaks, middle part falls out and rejoins after turning 180& Translocation: a section of a chromosome breaks off, attaches to another & Duplication: section of chromosome replicates & Non-disjunction: failure of sister chromatids to separate during anaphase

& Result in reshuffling of alleles on chromosome& Less important role in evolution (only reshufflement of alleles which already exist in same gene pool) & Eg Down’s Syndrome

Mutation

& Bring about changes in phenotype, allowing natural selection& Particularly important in asexually-reproducing organisms – only source of genetic variation& Mostly disadvantageous (useful ones are rare) & Natural selection prevents harmful mutation from accumulating, but ensures useful ones spread

S exual Reproduction (Meiosis) & Crossing over during meiosis & Combinations of gametes between individual

Why sex? & Making egg requires a lot of energy, and may be detrimental to organism& Sexual reproduction is energy consuming and risky& In terms of energy used, splitting of cells is better and less risky (can get variety through spontaneous

mutation)& Sex loses some good genetic sequences& BUT: Advantages of Variety > Risk of losing good genetic combination& Variety from sexual reproduction is much more than asexual& Variety is necessary to maintain and ensure survival& Necessary to combat disease – without sexual reproduction, a clonal species is vulnerable to increasing

parasitic attack& Sex helps purge the species of genetic mutations by shuffling genes in each generation

Speciation& Lineage splitting event, produces 2-3 more species & Same ancestral group split into different species

Geographic Isolation& 1 species goes through mutation& 2 groups of same species & Geographically isolated – don’t mix or interbreed, hence restriction of gene flow & Natural selection in each group – adapt to their own environments & Resulting in 2 different species

Allopatric Sympatric Geographical isolation2 groups separatedBoth groups evolve differently – 2 diff species

No geographic isolationSame place, but separated2 groups do not mix

Allopatric 1. Moving into new environments2. Geographical isolation

& Physical barriers& No more gene flow & Caused by environmental factors (Eg climate change, rise/fall in sea levels)

3. Different selection pressures

& Favour different traits which suit each environment & Favour organisms with better phenotypes (Eg better health, resistance to diseases, higher reproductive

rate) & Allele frequencies for certain genes change& Population takes on status of Subspecies (significantly different)

4. Reproductive isolation & Changes in genetic makeup and behavior patterns & No gene flow

Sympatric & Rarer than allopatric & No separation of gene pool by physical barrier & Same location, but because habitat is diverse, organisms occupy different niches after a while & Eg may live in the same tree, but different parts Niche Differentiation1. Niche Isolation

& Heterogenous environment (not the same everywhere) & Population exists within a diverse collection of microhabitats& Do not meet up with others from other microhabitats

2. Reproductive Isolation& Genetically isolated& Little interaction and interbreeding& No gene flow & Differences in behavior and physiology

Evidence for EvolutionPaleontology, biogeography, comparative anatomy, vestigial structures, embryology, molecular biology

Fossils & Can reveal immediate environment of an ancient organism, clues to a scene, even global change& Found in layers, so bottom = oldest & Best fossils are found in sedimentary rocks (formed from sediments such as sand/mud at bottom of ancient

seas)

Biogeography & Study of past and present distributions of plant and animal species & Darwin noticed that species all over the world are most closely related to those that live nearby – indicating

descent with modification from a common ancestor

Similar skeletal organization (comparative anatomy) Homologous structures Analogous structures Structures in different organisms that have a similar function and same origin (same vertebrae ancestor) Eg Pentadactyl limb Adaptive Radiation: basic limb plan has been adapted to

Structures that have similar functions, but from different origins Eg Bat wing (limb) vs Butterfly wing (not limb)

meet requirements of different niches

Embryo Resemblance & Similar embryo& Developed into the different parts of the body of each organism

Vestigial Organs & Structures with little or no known function that are thought to be remnants of a structure that at one time had

a function in an ancestral species & Eg Tail bone

Amino Acids& The less amino acid differences from man, the more similar & Shared a more recent common ancestor

Micro and Macro EvolutionMicro Macro & Changes in traits within population& In response to selection pressures& Resulting in changes to phenotype of population & Based on Darwinian theories of changes in allele

frequency due to natural selection within a species & Eg Antibiotic resistance in bacteria & Leads to MACRO

& Refers generally to formation of major groups of organisms from other groups that are distinctly different

& Eg Evolution of whales from terrestrial mammals & Mechanism is the same as MICRO & But carried on accumulatively over many millions of

years, resulting in the ever-increasing diversity of life we see today

Antibiotic Resistance of Bacteria& Simple organisms like bacteria and viruses evolve very quickly, because they reproduce so fast (numbers

double every 20 mins) & Bacteria have different antibiotic resistance genes in their chromosomes and plasmids & Able to exchange genetic material with one another, as well as with bacteria of different species & Mechanism allows antibiotic resistance genes to be passed on to other bacteria & In a bacterial population, there is variation and a very small proportion of the bacteria has antibiotic resistance

genes (caused by mutation)

& If patient does not finish entire antibiotic course prescribed, not all the bacteria will be wiped out & Those that survive would be those that are resistant, or tolerant of that antibiotic& Bacteria rapidly divides, and soon body will fall under infection by antibiotic-resistant bacteria & Change in allele frequency and traits of the population to being antibiotic resistant is an example of micro-

evolution

Phylogenetic Classification& All life is related& Divided into 3 major clades: Archaea, Bacteria, Eukaryota & Clade: grouping that includes a common ancestor and all its descendants

Tree, not Ladder1. Evolution produces a pattern of relationships A B C D among lineages that is tree-like, not ladder-like.

1. Just because we tend to read phylogenies from left to right, there is no correlation with level of "advancement."

1. For any speciation event on a phylogeny, the choice of which lineage goes to the right and which goes to the left is arbitrary. The following phylogenies are equivalent:

Misconceptions about humans& Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a

recent common ancestor that was neither chimpanzee nor human.& Humans are not "higher" or "more evolved" than other living lineages. Since our lineages split, humans and

chimpanzees have each evolved traits unique to their own lineages.

Linnaean Phylogenetic Ranks organisms in a hierarchy Provides evolutionary relationships Depends on morphology Molecular analysis can be used