Biology Book

Plants and Animals 05/02/09

DEFINITIONS All the external conditions, both abiotic and biotic, affecting organisms. Environment Where an organism lives, which generally has a particular environment. Habitat A biological community and the physical environment associated with it. Ecosystem The role of a species in its habitat or everything that it does, including its requirements (its total use of biotic and abiotic resources). Niche The non-living (physical and climatic) aspects of an environment. Abiotic factor Aspects of an environment due to the presence of living organisms. Biotic factor Range of values for an environmental factor within which a species thrives and reproduces. Optimum range The ability of an organism to withstand extreme variations in environmental conditions. Tolerance Any change in the structure or functioning of an organism that makes it better suited to its environment. Adaptation The group of plant, animal and micro-organism species inhabiting a given area. Community ENVIRONMENT The environment includes all the factors, both living (biotic) and non-living (abiotic), that affect the lives of organisms. BIOTIC FACTORS These include all the relationships between members of the same species (intraspecific) and with members of other species (interspecific). ABIOTIC FACTORS These are the physical factors in the environment that can act as stimuli for a response from an organism. EXAMPLES OF BIOTIC AND ABIOTIC FACTORS BIOTIC:

ABIOTIC:

Competition Aggression Co-operation Predator/Prey Reproduction Courtship Availability of mates Succession Stratification Hierarchies Parental care

Light Gravity Temperature Water Chemicals Touch Sound Pressure Wind Substance Current

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Plants and Animals 09/02/09

MATCHING PREFIXES PHOTO: Light CHEMO: Chemical HYDRO: Water GEO: Gravity THIGMO: Touch THERMO: Temperature RHEO: Current

PLANT RESPONSES TROPISMSThis is a growth response towards or away from an environmental stimulus (e.g. light, water etc.) coming from one direction. If the growth is towards the stimulus we say it is positive If the growth is away from the stimulus we say it is negative Examples of Tropisms: - If the shoot of a plant grows toward the light it is positively phototropic. - If the root of a seedling grows down it is positively geotropic. - If the roots in soil grow away from copper pipes they are negatively chemotropic. - If the branches of a vine twist around a trellis it is positively thigmotropic. - When a pollen tube grows towards a chemical in the egg it is positively chemotropic. 10/02/09

HYDROTROPISM OF SEEDLING ROOTS. AIM: To investigate the influence of moisture on direction of root growth. HYPOTHESIS: I think that the roots will grow towards the water.

GEOTROPISM OF BEAN ROOTS. AIM: To investigate whether gravity alone causes roots to grow downwards. HYPOTHESIS: That they will grow downwards no matter what direction the dish is turned.

NASTIC RESPONSES

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Plants and Animals This is the movement of plant organs in response to external stimuli. The movements are independent of the direction of the stimuli. Examples of such stimuli include temperature, light and humidity. Nastic movements are classified according to the nature of the stimulus. For example: PHOTONASTY: The response to alterations in the light intensity (opening of primrose flowers in the evening). THERMONASTY: The response to changes in temperature (opening of crocus and tulip flowers when the temperature increases). HAPTONASTY: The response to being touched (the folding up and drooping of Mimosa leaves when touched). Nastic movements can be distinguished from tropisms as they are usually more rapid, often reversible, and their direction is independent of the stimulus direction. Nastic responses are spontaneous and much faster when compared to tropisms. 12/02/09

PLANT HORMONES, NUTRITION AND TRANSPORT -

A hormone is any chemical produced in one part of the body that has a target elsewhere in the body. Plants have five classes of hormones. Animals, especially chordates, have a much larger number. Hormones and enzymes serve as control chemicals in multicellular organisms. One important aspect of this is the obtaining of food and/or nutrients.

AUXINS: - Auxins promote stem elongation, inhibit growth of lateral buds (maintains apical dominance). - They are produced in the stem, buds and root tips. E.g. Indole Acetic Acid (IAA) - Auxin is a plant hormone produced in the stem tip that promotes cell elongation. - Auxin moves to the darker side of the plant, causing the cells there to grow larger than corresponding cells on the lighter side of the plant. - This produces a curving of the plant stem tip toward the light, a plant movement known as phototropism. - Auxin also plays a role in maintaining apical dominance. - Most plants have lateral (sometimes called axillary) buds located at nodes (where leaves attach to the stem). - Buds are embryonic meristems maintained in a dormant state. Auxin maintains the dormancy. - As long as sufficient Auxin is produced by the apical meristems, the lateral buds remain dormant. - If the apex of the shoot is removed (by a browsing animal or a scientist), the Auxin is no longer produced. - This will cause the lateral buds to break their dormancy and begin to grow. In effect the plant becomes bushier. - When a gardener trims a hedge, they are applying apical dominance. GIBBERELLINS:

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Plants and Animals

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Gibberellins promote stem elongation. They are not produced in stem tip. Gibberellic acid was the first of this class of hormone to be discovered.

CYTOKININS: - Cytokinins promote cell division. They are produced in growing areas, such as meristems at tip of the shoot. - Zeatin is a hormone in this class, and occurs in corn (Zea). ABSCISIC ACID: - Abscisic acid promotes seed dormancy by inhibiting cell growth. - It is also involved in opening and closing of stomata as leaves wilt. ETHYLENE: - Ethylene is a gas produced by ripe fruits. Why does one bad apple spoil the whole bunch? - Ethylene is used to ripen crops at the same time. Sprayed on a field it will cause all fruits to ripen at the same time so they can be harvested. AUXIN AND PHOTOTROPISM A

Abiotic response is detected in the tip. B

Agar is water-based. Auxin is water-based and can dissolve in water-based things but not fat-based. C

Auxin is made in the tip and moves to the shaded side. D

Auxin travels down one side, that side being the side that elongates. Stimulus: Light

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Plants and Animals Chemical signal/Messenger: Hormone Hormone involved in phototropism: Auxin 1) Stimulus is detected in the tip of the coleoptile. A 2) Auxin is produced in the tip of the coleoptile. C 3) The Auxin passes down the shaded side. C 4) The Auxin causes cells to elongate. C,D 5) Auxin can be produced in darkness. D 6) Light initiates the response. A 7) Light stimulates the redistribution of Auxin. C.D 8) Auxin does not need intact cells to move from the tip to the stem. D 9) Auxin can move through water soluble chemicals. B 10) Uneven distribution of Auxin in the coleoptile causes bending. C ANIMAL RESPONSES TO THE ABIOTIC ENVIRONMENT Animals use a variety of environmental cues to orient and navigate as they move from one place to another. These behaviours are important as they affect the distribution of animals. Taxes and kineses are examples of orientation behaviour. A taxis (plural taxes) is a movement toward or away from a stimulus. For Example: Maggots show negative phototaxis after feeding, automatically moving away from light; this simple response ensures that the maggot keeps safe, away from potential predators. A kinesis involves a change in activity rate in response to a change in the intensity of a stimulus. In contrast to a taxis, a kinesis is randomly directed; once the animal has reached a favourable environment, their random movement slows down and they tend to remain in that environment. Orthokinesis: The speed of the movement is related to the intensity of the stimulus. Klinokinesis: The amount of random turning is related to the intensity of the stimulus. Examples of Taxes Positive Phototaxis: movement of unicellular algae towards light. Negative Phototaxis: movement of earthworms away from light. Positive Chemotaxis: movement of flatworm towards meat. Positive Thermotaxis: movement of mosquitoes towards heat. 18/02/09 During the migration of zebra across the African planes, they are vulnerable to predators.

ANIMAL MIGRATION WHAT is migration? - Active movement in a particular direction by a population of animals. - Regular, annual or seasonal. - To a feeding and/or breeding ground. - Usually a two way trip (there and back). - Often a long distance. - Often occurs at a certain stage in a life cycle. WHO migrates?

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Plants and Animals Birds. Salmon, Eels and Whitebait. Humpback Whales. Monarch Butterfly. Zebra.

WHY -

do animals migrate? Reproductive and survival success for example. To follow the summer. Triggers:  Maturation  Drop in temperature  Shortened day length  Genetic drive (innate) or endogenous circadian rhythms

HOW -

do animals navigate? Piloting, visual clues. Compass orientation. Sense of timing. Solar and star navigation. Chemical navigation. Sound. Waggle dance in bees. 24/02/09

BIOLOGICAL CYCLES PERIO D 12.4 hours

BIORHYTH M Circatidal

24 hours

Circadian

NATURAL CYCLE Tidal activity period Daily

14.8 days

Circasemilu nar

Spring tides

29.5 days

Circalunar

Lunar month

365 days

Circannual

Year

EXAMPLES -

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Activity, feeding and mating of Tidal organisms. Shell opening of tidal molluscs. Diurnal: Active during the day. Nocturnal: Active during the darkness. Crepuscular: Active at dawn and dusk. Whitebait mating above the high spring tide mark. Grunion (fish) mating at spring tides. Mating of many aquatic organisms. Human females: Body temperature, hormone levels, psychological state, reaction time. Mating seasons in many animals. Hibernation and aestivation. Migration. Photoperiodic responses in plants e.g. flowering. Dormancy. 3/03/09

VERNALISATION Many seeds require a period of cold before they will germinate.

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Plants and Animals

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To slow down their metabolism. So they know that it’s the right season to germinate.

DORMANCY Many seeds enter a period of metabolic inactivity after they have formed. ABSCISSON (LEAF FALL) - May be seasonal. - May follow accidental wind damage, animal browsing or drought. - Prevent water loss, parasite invasion at the place where the leaf was attached/ GROWTH FORMS 1) ANNUAL PLANTS: a. These grow, set seed and die in one year. 2) BIENNIALS: a. Grow, store food in the first year, then go through a period of chilling during the winter and flower the next year. They need vernalisation in order to flower. 3) PERENNIALS: a. These are plants that grow for a number of years. Many perennials are adapted to have a stage that dies down to survive over winter. This process is called OVER-WINTERING. EPHEMERALS These plants grow in semi- deserts. They germinate, grow, flower, set seed and die in a very short time. These plants have a chemical that inhibits germination. The chemical is water-soluble, but is only washed out of the seeds if there is sufficient rain. THE FIRE FACTOR: Lightning causes hundreds of fires every year. Fires can be confined to: - GROUND FIRES: in accumulations of litter or peat. - SURFACE FIRES: which sweep through herbs and shrubs. - CROWN FIRES: which travel through the true canopy. Ground and crown fires are usually disastrous, but some plants survive surface fires. In environments with a very dry season, some plants have become adapted to the fire factor. 1) Some plants have seeds that remain dormant unless their pods or cones have been cracked open by fire. This happens with many of the Australian outback nature plants. 2) Some trees, such as cork oaks, have such thick bark that they are protected from all but the hottest fires. 3) Some trees produce buds and woody tubers after fire destroys the old ones. 4) Fire-resistant species increase in abundance after fires, because of reduced competition. 5) Fires open up the canopy, so sun-loving plants can grow on the ground until the taller trees become re-established. 6) In very dry areas, the normal decomposers (bacteria and fungi) cannot get established because they need water. In these conditions, fire releases minerals from dead leaves and litter and makes them available for the plants, thus increasing the fertility of the soil. 7) Fire burns off the dead litter on grazing lands and allows animals access to new green shoots.

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Plants and Animals 8) Many grasslands owe their continued freedom from forestation to burning – the shrubs are destroyed by fire while the grasses survive.

FLOWERING IN PLANTS A plant knows that it is the right season to flower by the changes in the day/night length. (Photoperiod- Light length) Short day plants (long night plants) Produces flowers when the photoperiod is less than a certain critical day length (CDL). For example, if the CDL is 10 hours the plant will only flower if the dark period exceeds 14 hours. E.g. a short day species with a 10 hour CDL will flower only if the dark period exceeds 14 hours (24-10= 14hours). That is, these plants are prevented from flowering if they experience more than a certain number of hours of daylight. Long day plants (short night plants) Require a photoperiod that exceeds a certain CDL. E.g. in temperate climates, these plants flower in summer; Lettuce and petunias. They measure the shortening nights and flower when these become brief enough. Long day/Short night Plant germination is dependent on the length of night. For example, long day plants flower when the length of day is longer than the “critical day length”. Certain concentrations of pigments are converted when the plants flower. Pr (during the day) is converted to Pfr and the concentration of Pr goes down; therefore signalling to the plant that it is time to germinate. Day neutral plants These plants are unaffected by photoperiod. E.g. Many tropical plants and temperate plants such as tomato, carnation and dandelion. Red light (wave length 650-660nm) was found to be the most effective in preventing flowering in short day plants and enduring flowering in long day plants. It was also discovered that far red light (725-750nm) flashed straight after red light cancelled out the effect of the red light. No matter how many flashes of light are given, the wavelength of only the last one affects the plants measurement of night length. Thus, a succession of light flashes with the sequence R-FR-R prevents short day plants from flowering but flowering occurs if the sequence is R-FR-R-FR. As expected, the opposite behaviour occurs in long day plants. A pigment named phytochrome triggers the plant response to the length of night and day. Phytochrome exists in two forms: P665 or PRed or P AND P725 or PFar-Red or PFR

MATING SYSTEMS POLYGAMY

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Plants and Animals

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Many mating partners.  POLYGYNY • 1 male, many females.  POLYANDRY • 1 female, many males.  POLYGYNANDRY • Multiple mating, promiscuity.

MONOGAMY - Partnerships for a season or for life. POLYGAMY

BENEFITS Spread genes.

MONOGAMY

Help with caring for kids.

COSTS A lot of effort to make eggs/sperm, STIs. A lot of effort on both parts to take care of kids. A lot of effort goes in to courtship.

INTRASPECIFIC CO-OPERATIVE BEHAVIOUR Intraspecific co-operation behaviour includes: a) Group formation. b) Courtship and pair-bond formation. c) Parental care.

GROUP FORMATION -

BENEFITS: Hunting: o Many animals (wolves, lions, wild dogs) work as a team while hunting. o In wild dog packs, male (all) dogs work as a team to bring down a large prey. They eat, and then refill their stomachs to regurgitate to the puppies and nursing females. o Wolf packs hunt by having some circle the prey while others drive them forward. Another technique is to separate the young or crippled. o Farmers use these techniques with sheep dogs for rounding up sheep.

HOME RANGE vs. TERRITORY TERRITORY: Any geographical area that an animal consistently defends against members of the same species (and occasionally, animals of other species). Animals that defend territories in this way are referred to as territorial.

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Plants and Animals

HOME RANGE: The area that an animal traverses (moves around in) for its normal requirements of food, water and cover. The relative size of an animal’s territory is an indicator of its fitness. A large territory means the animal has greater fitness (superior ability to survive and reproduce in its environment due to its adaptations). A larger territory will also mean greater access to resources, which in turn will increase the reproductive fitness of that animal. In this way genes that carry on advantage, are passed on to offspring, increasing the chances of survival of those animals (and the species). Territorial disputes are generally settled by ritualised aggressive behaviours, which occasionally result in a fight.

MIGRATORY BIRD BEHAVIOUR BAR-TAILED GODWIT: - Migrate from Alaska to NZ, to Korea/China, back to Alaska. - Feeds in NZ, stores fat and protein before taking off to migrate. - Goes through three stages before migrating. • Gets rid of flight feathers/grows new ones. - Breed in Alaska. - NZ: Moult and feed, nutrients in mud flats, dependent on tides. - Colourful plumage – act to attract mate. - Innate behaviour – the birds instinctively migrate/know how to fly.

INTERSPECIFIC AGGRESSIVE RESPONSES: -

Competition between animals: for food, water, space and breeding sites.

PREDATOR-PREY RELATIONSHIPS: - Belligerent. - Most predators tend to catch the least well adapted, sick or old. • Keeps gene pool of prey strong. - Two species are dependent on each other’s wellbeing. • Predator that wipes out its prey is cutting off its own food source. - Predator-prey graph: pray always has a higher population and precedes the predator. - Three major variables: 1) Density, size and reproductive rate of prey. 2) Variation in predator-prey ratios for different prey species. 3) Possible difference in what the predator might eat if there was plenty of food, compared to what it actually does eat. FACTORS: 1) ENERGY BALANCE: not profitable if animal uses up more energy in the hunt than it can retrieve by eating carcass. 2) WEATHER: in warm weather, less energy is expended by mammals in keeping warm. i. E.g. lions need less food than wolves. 3) SIZE: larger animals tend to eat less food per unit weight. 4) ENDURANCE: cats in general, lack the endurance of animals like wolves. While wolves are always hunting, lions sleep 22hours a day. 5) SOCIAL SYSTEMS: male lion may expend no energy in a hunt.

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Plants and Animals 6) SIZE OF THE PREY: if a group of hunters can bring down a large animal and share the carcass, the energy expended would be worthwhile. Small preys are for individual kills. ADAPTATIONS FOR GETTING FOOD: Three main ways: 1) Letting the prey come to the predator. a. Sifting the environment. b. Dangle bait.

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Patterns of Evolution

PATTERNS OF EVOLUTION VARIATION: Stuff that’s different. - What causes variation?  Crossing over/recombination. EVOLUTION: Change in species over time. NATURAL SELECTION: Mode of Evolution.

NATURAL SELECTION INVESTIGATION AIM: To investigate the effect of variation in a characteristic, on natural selection in a hypothetical population. METHOD: 1) Cut out 50, 1 squares of... i. Newspaper. ii. White paper. iii. Coloured paper. 2) Sprinkle the squares onto a background piece of paper. This is your habitat. 3) The colour of my habitat is white. 4) In one minute pick up as many squares as you can. 5) Re-sprinkle the squares and repeat this method two more times. RESULTS: NEWSPAPER

TRIAL: 1 2 3 AVERA GE

WHITE

COLOUR

DISKS PICKED UP 8

SURVIVO RS 42

DISKS PICKED UP 24

SURVIVO RS 26

DISKS PICKED UP 7

SURVIVO RS 43

10

40

10

40

8

42

6

44

14

36

2

48

8

42

16

34

6

44

CONCLUSIONS AND QUESTIONS: 1) What characteristic of the population was being selected for or against in this investigation? 2) Write a conclusion linking natural selection and the characteristic you have identified. 3) Give an example of this situation in a real population. 4) Explain what would happen if you changed the colour of the habitat. 5) Briefly explain what is meant by “survival of the fittest”. 6) Is the colour of the background biotic?

WHAT CAUSES CHANGE IN GENE POOLS? There are 5 evolutionary agents: - Non-random mating.

Patterns of Evolution

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Mutation.  Changes in the DNA either random or by mutagen. Genetic drift.  Change in allele frequencies in small populations. Gene flow.  Immigration and emigration.  Founder effect and Bottleneck effect. Natural selection.  Stabilising selection – favours the mean.  Directional selection – favours one extreme.  Disruptive selection – favours both extremes over the average.

GENETIC DRIFT: Is the change in the gene pool of a small population due to chance. FOUNDER EFFECT: If only a few individuals move into a new area, they may only have a few of the available genes from the gene pool of that species. Thus isolated species descended from these ‘founder’ ancestors may have very different genes from the parent populations elsewhere. BOTTLENECK EFFECT: Disasters such as fire, floods and earthquakes can reduce a population to just a few survivors. Often the deaths are completely at random, so the small number of survivors is not really representative of the original gene pool. Some alleles will be above the normal number and some may be lost altogether. Bottlenecking, and the genetic drift that follows reduces the genetic viability in the population. STABILISING SELECTION: Favours the average over the extremes.

DIRECTIONAL SELECTION: Favours one extreme over the average or the other extreme.

DISRUPTIVE SELECTION: Favours both extremes over the average.

SPECIATON AND ISOLATING MECHANISMS

Patterns of Evolution

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A species is a reproductive community within which gene flow can occur; different species are genetically separated and unable to interbreed. A species often exists as a number of populations called demes. Where these vary across their range but interbreed at their boundaries they form a cline. A cline in the form of a semi circle or ring is called a ring species. For speciation to occur, populations must be separated by geographical barrier or by reproductive isolating mechanisms, so that gene flow is prevented. Allopatric speciation occurs when populations are separated in space by physical barriers such as mountain ranges. Reproductive isolating mechanisms will develop in geographically separated populations, which will eventually prevent any interbreeding. Sympatric speciation can occur when populations living in the same area become genetically separate through ecological isolation or reproductive accidents. This may result in the evolution of separate species. Instantaneous speciation can occur through polyploidy.

REPRODUCTIVE BARRIERS Gamete + Gamete Pre mating Prezygotic Before mating Habitat differences Differences in breeding times Mechanical differences Behavioural patterns Biochemical incompatibility BIOGEOGRAPHY:

Zygote Post mating Postzygotic After mating Hybrid inviability Hybrid sterility Hybrid breakdown

Geologically separate areas tend to be inhabited by organisms that are similar.

MOLECULAR BIOLOGY: Evolutionary relationships between species are reflected in the small differences in their DNA and proteins. FOSSIL RECORD: The succession of fossils in strata can be aged to show the most primitive forms of life in the oldest layers. Fish tend to be in the oldest strata, then amphibians, then reptiles. Birds and mammal are found in the youngest strata.

HOMOLOGOUS STRUCTURES: Show similarity in characteristics resulting from common ancestors. The wing of a bird or bat, the leg of a dog or humans and the flipper of a whale are all pentadactyl.

Patterns of Evolution

COMPARATIVE EMBRYOLOGY:

The early embryonic stages of all vertebrates, is very similar, even though the adults are different.

VESTIGIAL ORGANS: Organs that have become reduced or have lost their function. For example, tail bone in humans, wing bones in kiwi and leg bones in snakes.

SPECIATION: Formation of a new species. ALLOPATRIC SPECIATION: When a species population is separated by a geographical barrier. SYMPATRIC SPECIATION: Occurs when a sub-population becomes reproductively isolated in the midst of the parent population. Populations are said to be sympatric if their ranges overlap. These are species of the same genus living together in the same area. ALLOPATRIC SPECIATION occurs in the following way: - Reduced selection pressure – a population moves into a new area free from competing species, predators etc. With many ecological niches unfilled. - A population explosion follows which results in increased variation as most offspring survive, so alleles that were previously selected against are now free to be expressed. - Migrations into new environments on the borders of the range give rise to sub-species with different natural selection pressures. - Geographical barriers arise between sub-species and races, giving rise to geographical isolation. - The isolated populations will experience different mutations that will not flow to the parent population. - Isolated populations will usually be exposed to different ranges. - Some of the isolated sub-species develop genetic and chromosomal differences that will no longer allow interbreeding with the parent population. They are now genetically isolated and thus, a new species. EVENTS LEADING TO THE EVOLUTION OF NEW SPECIES. a) b) c) d)

A single species population occupying a uniform environment. Migration into different environments given rise to racial differentiation. Geographic barriers lead to the geographic isolation of some subspecies. The developments of genetic and chromosomal differences no longer allow interbreeding with the parent population in the subspecies.

Patterns of Evolution

e) Further changes in the environment remove the geographic barrier and allow species and parent species to live side by side. They maintain their separate identity because they are separated by a reproductive barrier.

PATTERNS OF EVOLUTION DIAGRAM:

Time

Divergent

Parallel

Convergent

ADAPTIVE RADIATION IN NZ SPECIES: HEBE -

PLANTS: More than 80 species. None occur all over the islands. Restricted by adaptations to very specific areas. Most found in rocky sites. Original native: probably large shrub with normal-sized leaves. The flowers were probably racemes (flowering with no pattern). Only one type of bee, so environment did not change this feature. Today there are three main groups of Hebe.

LARGE-LEAFED HEBES: - Most like ancestral types. Large shrubs to small trees. - Un-toothed leaves (broad/narrow) but never overlap. - Flowers are long racemes, usually larger than the leaves. - Found in lowland scrub, on coast, in forest margins; not extreme areas.  EXAMPLES: Hebe elliptica, H. Salicifolia, H. Pubescens and H. Stricta. MEDIUM-LEAFED HEBES: - Show xeromorphic features.  Features help plant to withstand dry, and conditions with wind and cold. - Toothed, generally fleshy leaves. - Leaves flat or concave, short and closely set. - Flowers are spikes crowded together at the tips or lacers. - Found mainly in sub-alpine to alpine regions, mainly on rocks.  EXAMPLES: H. Hulkeana, H. Sibalpina and H. Rakaiensis. SMALL -

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LEAFED HEBES: Show adaptations to withstand cold and snow (dry). Able to survive harsh conditions of bare rock. Called the whipcords. Small and spreading generally. Leaves reduced to scales, overlapping and tough. Often have red of yellowish tinge.  Adaptation to fully utilise the lower light levels in shaded areas. Also protect them from the higher levels of UV light found at high altitudes. Roots are branching and general growth form is low and spreading.

Patterns of Evolution

Good for windy areas, also spreads plant out to collect as much sunlight as possible. Flowers generally have only a few short flower spikes, crowded near tips of branches.  EXAMPLES: H. Ciliolata (semi-whipcord), H. Epacridea, H. Tetragona (whipcord) and H. Cheesemanii. If whipcords grow in favourable areas they will grow to be large leaves. 

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NATURAL SELECTION Population has lots of variation. ↓ Best adapted survive. ↓ Survivors have offspring. ↓ Offspring inherit the adaptive features. ↓ New population has adapted features.

Nectar bats with varying tongue lengths. ↓ Nectar bats with long tongues are better adapted in areas with long flowers. ↓ Long tongued nectar bats survive. ↓ Survivors have offspring. ↓ New population have long tongues.

EVOLUTIONARY RATES For many years after Darwin’s death it was thought that a new species always took millions of years to evolve, showing a gradual transition from one species to another. This is called Gradualism. As knowledge of the fossil record increased, it became evident that for many organisms, evolutionary rates were not steady. There were long periods of little change punctuated by sudden bursts of rapid evolution called Punctuated Equilibrium. GRADUALISM: - Variation and selection that happens gradually. - Over a short period of time it’s hard to notice. - Small variations that adapt an organism slightly better to its environment are selected for. - Very gradually, over a long time, the population changes. - Change is slow, constant and consistent. PUNCTUATED EQUILIBRIUM: - Changes occur in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals. - Mutations are random changes in the DNA that are not inherited from the previous generation, but are passed on to generations that follow. - The species changes very rapidly over a few generations, and then settles down again to a period of little change. *DEMES: rings/subsets of species (only interbreed in overlapping demes).*

Biotechnology

BIOTECHNOLOGY GENE: We are all made up of Genes/Discreet section of DNA with a code for a protein. DNA: Deoxyribose Nucleic Acid (polar molecule). PLASMID: Circular pieces of DNA. BIOTECHNOLOGY: Living tools i.e. Bacterium. ENZYME: Molecule that has an active site; biological catalyst. -

‘DEOXY’ means ‘minus an oxygen’. DNA is more stable than RNA. Nucleotide is formed by joining a nitrogen base, with a 5-carbon sugar and phosphate.

This is only one side. The other side is the same, just travelling the other way.

RNA – Ribose Nucleic Acid. Nucleic Acid.

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DNA – Deoxyribose

Four bases: Adenine (A), Guanine (G), Thymine (T) and Cytosine (C). Rungs of the ladder are made up of two bases always:  Adenine with Thymine; (AT)  Guanine with Cytosine; (GC) The bases are held together with weak hydrogen bonds (three bonds between GC and two bonds between AT). One turn of the helix contains 10 nucleotides.

GMO – GENETICALLY MODIFIED ORGANISMS There are three main ways they can be produced: 1) Add a foreign gene. 2) Alter an existing gene. 3) Delete or “silence” a gene. TECHNIQUES vs. APPLICATIONS

Biotechnology

Techniques allow scientists to manipulate genetic material e.g. PCR, Gel Electrophoresis, Restriction enzymes...etc. Applications refer to how scientists decide to use techniques e.g. DNA Profiling, Genome analysis, Gene cloning...etc. RESTRICTION ENZYMES are molecular scissors that cut DNA at specific recognition sites. Recognition sites are a precise sequence of 4-8 base pairs and are often palindromes. Restriction enzymes leave either a blunt or sticky end. Blunt ends result from a restriction enzyme cut that leaves no exposed nucleotide bases. Sticky ends have an overhang of exposed bases. LIGATION is when DNA fragments cut by restriction enzymes are reassembled. Ligation occurs in two steps. Annealing is when two matching sticky ends bond through base pairing. DNA ligase (an enzyme) joins the cut pieces of DNA back together. POLYMERASE CHAIN REACTION (PCR) is a technique used by biotechnologists to amplify small fragments of DNA for use in various other processes. - A double stranded piece of DNA is heated to 98⁰C for 5 minutes. This causes the DNA to denature and the double strands separate. - Primers, free nucleotides and DNA polymerase are added to the sample. The sample is then cooled to 60⁰C for a few minutes and the primers anneal to the DNA strands. - The sample is incubated and complementary strands are created (by DNA polymerase) using each strand of the DNA sample as a template. - This process is repeated about 25 times; each time the number of templates doubles over the previous cycle.

Gene Expression

GENE EXPRESSION PROKARYOTES: -

No membrane bound organelles. Conjugation. Bacteria. Unicellular. DNA not bound by membrane. DNA not bound by proteins. Plasmids.

EUKARYOTES: -

Multicellular. DNA is wound around proteins in a chromosome structure. Membrane bound organelles. Nucleus.

Mitosis Differences - Growth and repair. - Reproduction in asexual organisms. - One division. - Two daughter cells. - Diploid (2) numbers. - Genetically identical.

Similarities - Cell division. - DNA replicates.

Meiosis Differences - Formation of gametes. - Two divisions, four daughter cells. - Haploid number, ⅟2 number of chromosomes. - All genetically different.

 A T G G C T A A T G C  Triplet RNA  U A C C G A U U A C G Codon tRNA A U G  Anticodon DNA

MUTATIONS -

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Any change in DNA sequence that is not immediately and properly repaired or any inherited change in the sequence of DNA. Mutations that occur in body cells cause cell death or cancer and are not passed on to the next generation. Mutations that occur in sex cells are passed on to the offspring (called mutants). Usually recessive. Majority of mutations give disadvantages to the organism that inherits them. Caused by mistakes in DNA replication or by mutagenic agents. Occur spontaneously. 2 main types:  Gene mutations: change in nucleotide coding.

Gene Expression

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Chromosome mutations: can effect• Number of genes on the chromosomes. • Number of chromosomes. • Number of sets of chromosomes.

BASE OR POINT MUTATIONS 1) SUBSTITUTION. - Single base changes, can alter codon but may or may not have an effect. E.g.: - GAA to GAG – no effect, same amino acid, and glutamic acid would be picked up. - GAA to GUA – would have profound effect, changing glutamic acid to valine (cause of sickle-celled anaemia). - Change to the ‘stop’ code would stop production of the polypeptide at the wrong place. - Change in a ‘stop’ code would cause the polypeptide to go on and on.

E.g.:

THE FAT CAT SAT ALL DAY  Normal THE FUT CAT SAT ALL DAY  Mutant

2) INVERSION. - Positions of two nucleotides are inverted. If it happens within a codon, only that amino acid will be affected.

3) INSERTION AND DELETION. - Adding or taking away a nucleotide causes a reading frame shift or frame shift mutation. Ribosomes are not very intelligent. They continue to read mRNA nucleotides three at a time, so from the mutation point on the wrong amino acids are picked up – usually rendering the protein useless. Not surprisingly, frame shift mutations are usually lethal. INSERTION:

Gene Expression

E.g.:

THE FAT CAT SAT ALL DAY  Normal ATH EFA TCA TSA TAL LDA  Mutant

DELETION:

Describe how non-disjunction causes aneuploidy in humans. - Non-disjunction occurs when two chromosomes are not separated properly during anaphase of meiosis and therefore the gamete ends up having either one more or one less chromosome. Once the zygote develops, it becomes a mutant with some sort of syndrome.

GENE-GENE DIHYBRID INTERACTIONS Mendel formulated two laws based on certain assumptions. 1) LAW OF SEGREGATION: i. An organism has two alleles for each trait. The alleles separate from each other when gametes form. 2) LAW OF INDEPENDENT ASSORTMENT: i. Alleles of different genes separate independently when gametes form. Gene-gene interaction (epistasis) occurs when the expression of one gene affects the expression of another gene; hence one feature is affected by two genes. COLLABORATIVE GENES (AaBb x AaBb gives 9:3:3:1) Alleles at two (or more) different gene loci produce distinct phenotypic effects, but when certain alleles are both present there can be yet another effect. In this case the phenotype is not affected by the number of copies of the allele present. There are typically four phenotypes. SUPPLEMENTARY GENES (EPISTASIS) (AaBb x AaBb gives 9:3:4) A dominant allele at one gene locus must be present for the expression of another gene. Typically there are three phenotypes. For Example: Coat colour in mice involves gene A (makes black pigment) and gene B (disperses pigment). For black coat colour, black pigment must be made and dispersed; for brown coat colour, black pigment is made but not dispersed; for white coat colour, black pigment is not produced (dispersal does not affect phenotype).

Gene Expression

COMPLEMENTARY GENES (AaBb x AaBb gives 9:7) In this situation the dominant allele of one gene can only be expressed if the dominant allele of another gene is present too. At least one dominant allele of each gene must be present. Typically there are two phenotypes. For Example: Sweet Pea Flower colour involves genes A and B. The genes control successive metabolic steps; hence the effect of gene B is dependent on the intermediary white coloured product associated with gene A. For purple flower colour, dominant alleles for both genes must be present. In other cases, the flower is white. DUPLICATE GENES (AaBb x AaBb gives 15:1) For two genes at different loci, if either of the dominant alleles is present, the trait is expressed (i.e. two different genes can produce the same phenotype). For Example: Fruit width in Sheppard’s Purse involves genes A and B. The two genes code for two different enzymes, both of which produce the active chemical that forms wide fruit. Therefore, there are two ways of getting wide fruit. Whenever A or B is present the fruit will be wide; aabb is the only genotype not to show the trait of wide fruit. MODIFIER GENES The expression of many genes can be altered to varying degrees by other genes. This can result in a range of different phenotypes. For Example: Eye colour is determined by the B (brown) and b (blue) alleles along with modifier genes that control the amount, tone and dispersal pattern of the iris pigment, which results in the additional phenotypes of hazel and green.

LINKED GENES (ON THE SAME CHROMOSOME) Start with a homologous pair of chromosomes carrying the linked genes:

Before meiosis, the chromosomes replicate:

The chromatids separate:

Only two kinds of gametes form:

Gene Expression

LINKED GENES WITH CROSS-OVER When the chromosomes line up as tetrads in meiosis, two chromatids (one from each member of the pair) may cross each other and break off, with the broken parts rejoining to the opposite chromatid. When the chromatids finally separate out into independent chromosomes, the ones with the new combination of alleles are called the recombinants, and this process is called crossing-over. If the original chromosome alleles are AB and ab, now the recombinants are Ab and aB. Linked genes on a pair of homologous chromosomes:

Replication takes place at the beginning of meiosis:

The homologous chromosomes undergo synapsis and crossover occurs between adjacent chromatids:

The chromatids separate:

Now four different gametes have formed. The ones in the middle that have exchanged pieces of chromosomes, i.e. have ‘recombined’, are called the recombinants (Ab and aB) and the ones that did not exchange pieces are called the non-recombinants (AB and ab). QUICK NOTES:

Gene Expression

64 codes for 20 amino acid therefore there is more than one code for each amino acid.  If there is a mutation, there will be another code to replace it. INTRON: Non-coding DNA. EXON: Coding DNA/has gene.

Human Evolution

HUMAN EVOLUTION PRIMATES – A SPECIAL MAMMAL HUMAN CLASSIFICATION KINGDOM PHYLUM CLASS ORDER FAMILY GENUS SPECIES

Animalia Chordata Mammalia Primate Hominidae Homo Sapiens

CHIMPANZEE CLASSIFICATION Animalia Chordata Mammalia Primate Hominidae Pan Troglodytes

MAMMAL CHARACTERISTICS - Suckle young on milk from mammary glands. - Viviparous (give birth to live young). - Intelligent, large skull. - External ear and three middle ear bones. - Four different types of teeth. - Homoeothermic (maintain constant body temperature) “warm blooded”. - Hair and sweat glands. - Four chambered heart. - Diaphragm. PRIMATE CHARACTERISTICS - Prehensile hands (and tails). - Nails and sensitive hands. - Pentadactyl (5 fingers). - Reduced sense of smell. - Collar bone. - Binocular, stereoscopic vision. - Good hand-eye co-ordination. - Large brain and eyes. - Tail. - Retina sensitive to low levels of light. - Wrist, elbow, shoulder and hip very mobile joints. - Hind limb dominated locomotion. - Oestrus cycle and two nipples. - Usually only one young per pregnancy. - Good sense of balance. - Upright sitting posture. - Social life (grooming, parental care, learning, breeding etc...). PRIMATE GROUPS

PROSIMIANS

PRIMATES

TASIERS

NEW WORLD MONKEYS

OLD WORLD MONKEYS

Squirrel and Spider

Baboon, Macaque

APES Orangutan, Gorilla, Chimpanzee (Great Apes), Gibbons (Lesser Apes)

ANTHROPOIDS HOMINOIDS

HOMININS Australopithecus Sp., Homo Sp. (Humans)