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The ventricles relax. Volume of the ventricles increases & so pressure in the ventricles falls. This risks the blood in the pulmonary artery & aorta flowing backwards into the ventricles. That tendency to flow backwards causes the semi-lunar valves at their bases to shut, preventing blood re-entering the ventricle. The atria also relaxes during diastole, so blood from the vena cavae & pulmonary veins enters the atria & cycle begins again.

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Atrial systole - the atrium walls contract & blood pressure in the atria increases. This pushes the blood through the tricuspid & bicuspid valves down into the ventricles, which are relaxed.
Ventricular systole - The ventricle walls contract & the increase in the ventricle. Forcing blood up through semi-lunar valves, out of the heart, into the pulmonary artery & aorta. The blood cannot flow back from the ventricles into the atria because the AV valves are closed by rise in he ventricular pressure. The pulmonary artery carries deoxygenated blood to the lungs & the aorta carries oxygenated blood to the rest of the body.

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The heart is seen as 2 separate pumps, one dealing with oxygenated blood & the other with deoxygenated blood. There are 2 relatively thin-walled collection chambers, the atria which, which are above 2 thicker-walled pumping chambers, the ventricles, allowing complete separation of oxygenated & deoxygenated blood.
The heart consists largely of cardiac muscle, a specialised tissue with myogenic contraction. Meaning it can contract & relax rhythmically, of its own accord. In life the heart rate is modified by nervous & hormonal stimulation. Unlike the voluntary muscles, cardiac muscle never tires.

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Double circulatory system is described as..

The pulmonary circulation serves the lungs. The right side of the heart pumps deoxygenated blood to the lungs. Oxygenated blood returns from the lungs to the left side of the heart.

The systemic circulation serves the body tissues. The left side of the heart pumps the oxygenated blood to the tissues. Deoxygenated blood from the body returns to the right side of the heart.

In each circuit the blood passes through the heart twice, once through the right side & once through the left side.

The double circulation of a mammal is more efficient than the single circulation of a fish because oxygenated blood can be pumped around the body at a higher pressure.

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The blood passes through the heart twice in its circuit of the body. Mammals have a closed circulation system. Blood is pumped by a muscular heart at high pressure, giving a rapid flow rate through blood vessels. Organs are not in direct contact with the blood but are bathed by tissue fluid, which seeps out of capillaries. The blood pigment, haemoglobin carries oxygen. Blood pressure is reduced in the lungs & its pressure would be too low to make the circulation efficient in the rest of the body. Instead the blood is returned to the heart, which raises its pressure again, to pump it to the rest of the body. Materials are then delivered quickly to the body cells.

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The blood more in blood vessels. There are 2 types:
Single circulation, the blood moves through the heart once in its passage around the body.

In earthworms, blood moves forward, in dorsal vessel, & back int eh ventral vessel. 5 pairs of 'pseudo hearts', thickened muscular blood vessels, pump the blood from the dorsal to ventral vessel & keeps it moving.

In fish, the ventricle of the heart pimps deoxygenated blood to the gills, where its pressure falls. Oxygenated blood is carried to the tissues & from there, deoxygenated blood returns to the atrium of the heart. Blood more to the ventricle & circulation starts again.

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The blood doesn't move around the body in blood vessels, nut it bathes the tissues directly while held in a cavity called the haemocoel.
Insects have an open blood system. they have a long, dorsal(top) tube-shaped heart, running the length of the body. It pumps blood out at low pressure into the haemocoel, where materials are exchanged between blood cells & the body. Blood returns slowly to the heart & the open circulation starts again. Oxygen diffuses directly to the tissues from the tracheae so the blood does not transport oxygen & has no respiratory pigment.

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Plants that live in extreme environments. They have thicker waxy cuticles to reduce evaporation, reduced leaf area(needles, spines), hair leaves as hairs trap a layer of saturated air, sunken stomata(pits above them become saturated).

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Gas exchange & water loss both happen through stomata, plants balance conflicting needs of gas exchange & control water loss. Stomata close..

At night, to prevent water loss when there is insufficient light for photosynthesis

in very bright light, as this generally is accompanied by intense heat, increasing evaporation

if there is excessive water loss

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Chloroplasts in guard cells photosynthesise, producing ATP; providing energy for active transport of K+ ions into guard cells from surrounding epidermal cells. Stored starch is converted to malate(a salt or water of malic acid). The K+ ions & malate ions lower the water potenial in the guard cell, water enters by osmosis. Cell walls are thinner in places. The cells explains as they absorb water but less so in the areas where the cell wall is thick. These areas are opposite each other on the 2 guard cells & as the cell stretches. A pore appears betwee these areas(stoma). At night, the reverse process happens & pore closes. Transpiration occurs through stomata. Sunlight on upper surface would increase evaporation, so confining stomata to lower surface minimises water loss.

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During the day if water enters the guard cells, they become turgid & swell, the pore opens. If water leaves the guard cells, they become flaccid, the pore closes.

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Cuticle - waxy & clear
Palisade mesophyll - lots of chlorophyll, closely packed
Spongy mesophyll - moist, allow CO₂ to be absorbed by palisade cells

Air spaces - allows O₂ & CO₂ to diffuse between stomata & cella

Guard cell - allow opening/closing & prevents waterloss(transpiration)
Xylem - transports water & minerals
Phloem - transport organic resources

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They are very efficient at gas exchange. Large SA relative to the body, gases dissolve in the moisture lining of the alveoli. The walls are made of squamous epithelium, 1 cell thick, diffusion path is short. An extensive capillary network surrounds alveoli maintaining the gradient. Capillary walls 1 cell thick. Deoxygenated blood enters capillaries, O2 diffuses out of the air in the alevoli into the red blood cell in the capillary. CO₂ diffuses out of the plasma in the capillary, into the alveoli where it is exhaled.

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Emphysema, chronic bronchitis & asthma. Makes breathing difficult, lungs become damaged & inflamed.
Symptoms include:
Lethargy, weight loss, tight chest, chesty cough, breathlessness, wheezing & fluid on the lungs. Causes include..
Smoking - harmful chemicals in smoke damage lung linings & airways, passive smoking also increase chances of COPD. Fumes & dust - chemicals at work can damage lungs. Air pollution - exposure for long periods can affect how well the lungs work.

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In cartilaginous fish, CO₂ diffuses from the blood into water. In bony fish, there is a counter-current system, CO₂ diffuses out of the blood among the whole gill lamellae. The is more effiejcnd than that of cartilaginous fish.

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They have gills in 5 spaces on each side(gill pouches) which open at gill slits. Their ventilation system is less efficient than bony fish, because...

Don’t have a special mechanism to force water over gills, so just keep swimming for ventilation to bappen

Blood travels through gill capillaries in the same direction as water, described as parallel flow. Oxygen diffuses from where it is most concentrated(in water) to lower conc. (in blood). This diffusion only happens until the conc. are equal

Oxygen conc. is limited to 50% if it’s possible maximum value

Gas exchange in parallel flow doesn’t occur across the whole gill lamella(only part of it) until both sides are in equilibrium

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Lungs of birds process large volumes of oxygen because flight requires a lot of energy. Birds do not have a diaphragm, but their ribs & fligh muscles ventilate their lungs more efficiently(air sacs) than the methods used by other vertebrates. These sacs don’t play a direct role in gas exchange, but to store air & act like bellows. Lungs can maintain a fixed volume.

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Lungs have a more complex internal structure than in amphibians, increasing the surface area for gas exchange. More efficient that amphibians, greater SA. Don’t have a diaphragm, lungs inflate/deflate by contraction of ribcage & intr costal muscles.

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Moist skin is permeable with a well-developed capillary network just below the surface. Gas exchange takes place through the skin & (when the animal is active) in the lungs too. Larvae(tadpoles) live in water & have gills. They go through metamorphosis to become adults & lose gills/develop lungs. Adults use their skin(when inactive/underwater) or lungs(when active) as gas exchange surfaces.

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Earthworms are terrestrial, they're cylindrical(SA:V ratio smaller than flatworm). It's larger than a compact organism with the same volume. It's skin is the respiratory surface which it keeps moist by secreting mucus(O₂ dissolved on a moist surface). It has a low oxygen requirement as it's slow moving & has a low metabolic rate(O₂ diffuses across skin & into blood capillaries beneath). Very basic circulatory system. Has a bumpy body to increase SA.

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Flatworms are aquatic organisms & being flat means they have a larger SA than spherical organisms of the same volume. Their large SA:V ratio has overcome the issue of size increase because no part of the body is far from the surface & so diffusion paths are short. Also they live in water so O₂ is already dissolved.

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Very small, cell membrane is thin so diffusion happens rapidly

Single cell is thin so diffusion distance is short

High SA:V ratio

Lives in water = O₂ already dissolved & moisture provided by habitat

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In larger organisms many cells re aggregated together. They have a lower SA:V ratio than smaller organisms. Diffusion across their surfaces is not efficient enough for their gas exchange.

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Single-celled organisms such as Amoeba are very small. Single cells have a large SA:V ration. The cell membrane is thin so diffusion in the cell is rapid. A single cell is thin, so diffusion distance inside the cell is short. Single cells can therefore absorb enough oxygen across the membrane to meet demands & remove carbon dioxide fast enough to prevent a high conc. & making cytoplasm too acid for enzyme function.

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Small pores on the above-ground parts of plants & occur mostly on the lower surface of leaves - mostly shaded & college so evaporation won’t take place as much. Each pore is bounded by 2 guard cells. Guard cells are unusual as they’re the only epidermal cell with chloroplasts & have unevenly thickened walls, with the inner wall next to the pore in many species being thicker than the outer wall. The width of the atoms can change & so stomata control the exchange of gases between the atmosphere & in the internal tissue of the leaf.

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Plants need to generate energy constantly, so they respire all the time. During the day, plant cells painting chloroplasts carry out photosynthesis. Some of the CO₂ needed for photosynthesis is provided from respiration. Some of the O₂ produced from photosynthesis is used for respiration too.
During the day, the rate of photosynthesis is faster than respiration, overall O₂ is released. At night, photosynthesis doesn't happen, so the gas released is CO2. Gases diffuse through the stomata down a concentration gradient. In the leaf, the gases in the sub-stomat air chambers diffuse through the intercellular spaces between the spongy mesopgyll cells & into cells. The directions of diffusion depends on the conc. of gases in the atmosphere & the reactions in the plant cell.

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Insects live in arid habitats, water evaporates from their body. leading t dehydration. Efficient gas exchange needs a thin, permeable surface, this contradicts what they need to conserve water. Many insects reduce water loss with a. waterproof layer(chitin exoskeleton). Insects have a relatively small SA: V ratio & even without the exoskeleton they couldn't use their surface to exchange enough gas by diffusion. Instead, gas exchange occurs through spiracles, running along the side of the body. The spiracles lead to a system of branched, chitin lined air tubes called tracheae, which branch into smaller tubes called tracheoles. The spiracles can open & close so gas exchange can happen & reduce water loss. The hairs covering spiracles in some insects contribute to water loss prevention & prevent particles getting in. When resting, they rely on diffusion through spiracles to take in O2 & remove CO2, During activity(flight), movement of the abdomen ventilate the tracheae. The ends of tracheoles are fluid-filled & close to muscle fibres(this is where gas exchange takes place). No respiratory pigment or blood circulation is needed(no heart). CO₂ diffuses out by the reverse process.

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Lungs are enclosed in an airtight compartment, the thorax

Pleural membranes line the thorax & cover each lung. Fluid between the membranes prevent friction between the lungs & chest cavity as the lungs move

At the base of the thorax is the diaphragm(dome shaped sheet of muscle), separating the thorax from abdomen

Rubs surround the thorax with intercostal muscles between ribs

tracheae is a flexible airway, bringing air to the lungs

2 bronchi are the branches of the trachea

lungs consist of a branching network of tubes called bronchioles, which arise from the bronchi

At the end of the bronchioles are alveoli

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Fish are active & need a good oxygen supply. Gas exchange takes place across a special respiratory surface, the gills. Gills have:

A one-way current of water, kept flowing by a specialised ventilation mechanism

Many folds, providing large SA which water can flow over & gases exchanged

Large SA, maintained as the density of water flowing through prevents the gills collapsing Ono each other

2 main groups of fish(different material composing the skeleton) cartilaginous & bony fish. They ventilate their gills in a different way

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Water evaporates from body surfaces, could result in dehydration

Surfaces must be thin & permeable with a large SA. Water particles are small & pass through gas exchange surfaces, meaning they’re always moist which could bead to water loss

Animals have evolved different methods of overcoming the conflict of needing to conserve water. Gills cannot function out of water but, the reaches of insects & lungs of vertebrates do. Lungs are internal, minimising water loss & heat.

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Plants lean/grow towards the sun

Roots grow down into soil

Vines climb trees to get sunlight

Polar bears dig dens to protect them from cold winds

Mating ritual such as displaying a peacock's tail or the elaborate dance performed by flamingos, increasing an animals chance of reproduction

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Leaves fall off deciduous plants when temperature & light intensity decreases. Without leaves, plants can't lose water through transpiration & risk dehydration, also surviving winter

Mammals & birds are endothermic & avoid wasting energy trying to maintain body temperature in the cold. During hibernation, a polar bear resets its body thermostat to use less energy & the body temp. drops to 2°C, rather than staying at 37°C.

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Sharks, dolphins, penguins have streamlined bodies making them more efficient when catching food & escaping predators

Some plants with honey or nectar guides(beeline). Indicating the centre of flowers, source of nectar & pollen, Without them, fewer insects would be attracted to them.

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Mutations - difference in DNA

Variation - different physical appearance/behaviour

Competitive adaptions - outcompete others for resources

Survival of the fittest - more suited to environment

Reproduction - more suited = more offspring

Pass advantageous alleles onto offspring - inherit genes, so more suited to environment

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DNA finger printing - molecular assessment

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DNA finger printing - molecular assessment

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More closely related organisms have DNA base sequences that are more similar. The DNA doesn't all code for protein; like all DNA, non-coding sequences undergo mutation so individuals can acquire different base sequences.

Single base differences, called SNPs(single nucleotide polymorphisms)

Regions of DNA that vary, 20-40 base sequences long, often repeated many times called HVR(hyper-variation regions) or STRs(short tandem repeats)

The more HVRs & STRs there are, the more differences there are in the DNA fingerprint, indicating greater biodiversity.

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Polymorphic loci - assessment of biodiversity

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Polymorphic loci - assessment of biodiversity

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Number of alleles - a genes position on a chromosome is its locus. A locus shows polymorphism if it has 2+ alleles. If a gene has more alleles, its locus is more polymorphic than if there were fewer.
Proportion of alleles - Considering the whole gene pool, & 98% of all alleles of a particular gene are the same recessive allele, there is low biodiversity for that gene. But if only 50% of the allele was recessive then the other 50% would be other alleles, making the biodiversity higher.
E.g the ABO blood grouping system in humans. The I gene has 3 alleles IA IB IO

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Many organisms are used to support human life, staple foods(wheat, corn), medicines(penicillin - fungus) & raw materials(cotton, rubber).
Reducing biodiversity reduces the uniqueness of the environment.

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Mass extinction followed by radiation of a new species. An example is the demise of the dinosaurs & trees ferns largely as a result of climatic, geographical & biological changes.
Bottlenecks: earthquake, drought, deforestation, new species introduced, human activity, nuclear winter.

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N - total number of species
n - number in each species
Answer is between 0 & 1
Σ - differences between

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1. Succession: over time a community of organisms change their habitat(niche), making it more suitable for other species. It increases animal biodiversity, but decreases animal biodiversity(picture)
2. Natural selection.
3. Human influence: in many places human activity has made areas less hospitable to living organisms. It has decreased their biodiversity & led to extinction.

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most diverse habitats are in the rain forests and coral reefs

number of species per km2 increases moving from the equator to the pole

most plats grow at high light intensity, more plants support herbivores & therefore more carnivores

equatorial regions have more energy flowing through their ecosystems than polar regions = greater biodiversity in equatorial regions

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Biodiversity refers to 2 aspects of organisms in a given environment.
1. the number of species, sometimes called 'species richness'
2. the number of organisms within each species

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morphological definition - if 2 organisms look similar they are likely to be the same species, 'sexual dimorphism'(e.g mane on male lions) must be taken into account.
Reproductive definition - they can interbreed to make fertile offspring.

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Proteins are usually displayed as bands on an electrophoresis gel. Biochemical methods can reduce the mistake made in classification due to convergent evolution. The degree off similarities in the amino acid sequence of the same protein in 2 species will reflect how closely related they are.

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The 35 animal phyla include a great range of body plans. Most are motile(capable of movement) at some stage in their life cycle.

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Yeast are single-celled

Moulds such as Penicllium and mushrooms such as Amanita muscaria have hyphae that weave together to form the body of the fungus, a mycelium. In some, cross-cell walls, called septa, sub-divide the hyphae.

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Mosses, horsetails & ferns reproduce with spores

Conifers & flowering plants, which reproduce with seeds.

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Some have only 1 cell & these are major component of plankton. Others are colonial. Some e.g Spirogyra, have plant-like cells. Some e.g Amoeba, are animal-like cells. Some e.g Euglena, have cells with characteristics of both plant & animal cells.

Some have many similar cells. These are the seaweeds, or algae, such as the sea lettuce, Ulva lactuca.

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Prokaryota are microscopic. This kingdom contains all the bacteria & cyanobacteria (previously called blue-green algae).

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The proteins of different species an be compared using immunological techniques. If you mix the antigens of one species, such as blood protein albumin, with specific antibodies of another, the antigens & antibodies make a precipitate. The closer the evolutionary relationship, the more the antigen & antibody react & make more precipitate.

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The sequence of amino acids in proteinsis  determined by the DNA base sequence. The degree of similarity in the amino acid sequence of the same protein in 2 species will reflect how closely related they are.

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Comparing the DNA base sequences of 2 species. To work out how closely related two species of primates are e.g humans & chimpanzees. DNA from both is extracted, separated & cut into fragments. The fragments from the 2 are mixed and, where they have complimentary base sequences, they hybridise together. Organisms can have comeplete, partial & no hybridisation.

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Biochemical methods measure the proportion of genes or proteins shared between species to estimate relatedness.

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Homologous structures have the same common origin but serve a different function. Analogous structures have the same function but a different origin. The dolphin & penguin have modified pentadactyl limbs(homologous). Whereas the shark does not(analogous).
Convergent evolution is where structures evolved similar properties(wings of birds & bats) but have different functions. Divergent evolution is the process of 2 or more related species becoming more & more dissimilar.

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The theory of evolution suggests that organisms share a common ancestor. The more similar 2 organisms are the more recent they are assumed to have diverged (separated). Likewise, organisms with little in common may have diverged much earlier from a common ancestor.

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Carl Linnaeus developed a two-part naming system. The first part of the name indicates the group the organism belongs to(genus) and the second part indicates the species. The names became the standard way all scientists can identify species, and communicate with each other about them.

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A taxon is any group within the system of classification. Bigger taxa contain smaller taxa. All organisms belong to 1 of 3 domains & are defined on the basis of rRNA base sequences & similarities in the DNA base sequence.
Eukaryote - plantae, Animalia, fungi, protoctista
Archaea - bacteria(prokaryotes) with unusual metabolism
Eubacteria - familiar bacteria such as E. coli & Salmonella

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A diagram showing evolutionary descent. Grouping closely related organisms together - groups having more recent ancestors with each other. If organisms are closely related they may show physical similarities.

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All 1 domain - Eukaryote:
Animalia
Plantae
Fungi
Protoctista
Split into archaea & eubacteria
Prokaryote
Organisms in different kingdoms have significant differences. A phylum is a sub-group of a kingdom

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Taxonomy - the identification & naming of organisms
Species - a group of organisms sharing a large number of physical features & able to interbreed to make fertile offspring
Phylogeny - the evolutionary development of an organ or other part of an organism
Morphology - the study of the size, shape & structure of animals, plants & microorganisms and the relationships of their constituent parts
Binomial - a 2 part name of a species of a living organism(a system of naming species in latin, e.g Homo sapiens - italics or underlined). Universal language

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Have the following features:

A suitable medium to carry materials

A pump, e.g heart, for loving blood

Valves to maintain the flow in one direction

Some systems have:

A respiratory pigment (haemoglobin) such as vertebrates & invertebrates, but not in insects, which increases the volume of O₂ that can be transported

A system of vessels with a branching network to distribute the transport medium to all parts of the body

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Diffusion happens across a respiratory surface. As the volume of an organism increases, the surface area does too. For rapid diffusion, a respiratory surface must have:

large SA:V ratio

thin membrane = short diffusion path

permeable, for easy diffusion of gases

a mechanism to produce steep conc. gradient across surface, by rapidly bring oxygen/removing carbon dioxide.

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Kingdom(keep)
Phylum(popping)
Class(class A's)
Order(or)
Family(family)
Genus(get)
Species(shot)

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They have an internal skeleton made of bone & gills are convered with a flap called the operculum, rather than opening directly on the side of the fish, as in cartilaginous fish. Bony fish live in both freshwater and seawater & are the most numerous of aquatic vertebrates.

Blood & water flow in opposite directions at the gill lamellae, maintaining the conc. gradient & therefore, oxygen diffuses into the blood. Along their entire length

More efficient because there is a constant conc. gradient(not always steep!)

Gas exchange can take place over the whole lamellae unlike in cartilaginous fish(only 50%)as blood & water are moving in the same direction