A: Classification (Higher in bold) Organisms can be classified into groups according to similar characteristics. The five Kingdoms are plants, animals, fungi, protoctista and prokaryotes. Some animals are difficult to place into distinct groups because there is so much variation. All organisms are classified into groups called kingdom, phylum, class, order, family, genus and species. The classification of species is important in terms of identifying evolutionary and ecological relationships between them. There are two classification systems: natural (based on evolutionary relationships) and artificial (for purposes of identification). There are two classification systems: natural (based on evolutionary relationships) and artificial (for purposes of identification). DNA sequencing information has led to changes in understanding of classification. Systems of classification change over time as scientists learn more information about DNA. Know characteristics of different classes of arthropod: insects arachnids crustaceans myriapods Evolutionary relationships between organisms can be displayed using evolutionary trees. Evolutionary relationships of organisms in a group can be modelled by analysing multiple characteristics and how this has been facilitated by ICT. Problems of classifying organisms into species: hybrids (are not a species because they are infertile) organisms that only reproduce asexually like bacteria still have different characteristics evolution as a continuing process so all organisms are constantly changing Organisms of the same species: may show great variation have more features in common than they do with organisms of a different species. Similar species tend to live in similar types of habitats. Species is a group of organisms which are capable of interbreeding to produce fertile offspring. The binomial system is an international basis for naming species to avoid confusion. Closely related species: share a relatively recent ancestor. may have different features if they live in different types of habitats. Similarities and differences between species can be explained in terms of both evolutionary and ecological relationships. E.g. similar species may have similar features because they are adapted to live in the same habitat.
B: Energy flow (Higher in bold) Trophic level means feeding level. Changes in the population of one organism may affect the other organisms in a food web. Green plants, algae and bacteria are producers. Some organisms are both primary and secondary consumers, they are called omnivores. Pyramids of biomass show the dry mass of living material at each stage of a food chain. Pyramids of numbers and pyramids of biomass for the same food chains can be different shapes. Some pyramids are difficult to draw: organisms may belong to more than one trophic level you have to kill organisms to measuring dry biomass. Energy from the Sun enters food webs by photosynthesis, it is passed on to organisms when they eat the plants. Some energy is transferred to less useful forms at each stage (trophic level) in the food chain, including: heat from respiration excretion egestion. Excretory products, faeces and uneaten parts can be used as the starting point for other food chains. The efficiency of energy transfer explains the shape of pyramids of biomass. As energy is transferred out of the food chain, there is less available to become biomass. The efficiency of energy transfer explains the limited length of food chains because as energy leaves at each link there is less left for the next organism. Calculate the efficiency of energy transfer. Efficiency = energy in biomass x 100% energy available
C: Recycling (Higher in bold) When animals and plants die and decay the elements in their bodies are recycled. Carbon is taken up by plants as carbon dioxide. Many soil bacteria and fungi are decomposers, which decay dead organisms. This decay process is important in making elements available again to living organisms. As animals and plants grow they take in chemicals and incorporate elements from these into their bodies. Two of the most important elements that are required are: carbon nitrogen. Recycling of nutrients takes longer in waterlogged or acidic soils than it does in well drained neutral soils because there is a lack of oxygen for the microbes, Carbon is recycled in nature, by: plants removing carbon dioxide from the air by photosynthesis feeding passing carbon compounds along a food chain or web plants and animals releasing carbon dioxide into the air, as a product of respiration burning of fossil fuels (combustion) releasing carbon dioxide soil bacteria and fungi, acting as decomposers, releasing carbon dioxide into the air. Carbon is recycled in nature, by: marine organism making shells made of carbonates shells becoming limestone carbon returning to the air as carbon dioxide during volcanic eruption or weathering oceans absorbing carbon dioxide, acting as carbon sinks. Nitrogen is taken up by plants as nitrates. The abundance of nitrogen in the air (78%). Nitrogen gas can t be used directly by animals or plants, because it is unreactive. Nitrogen is recycled in nature, by: plants taking in nitrates from the soil to make protein for growth feeding passes nitrogen compounds along a food chain or web nitrogen compounds in dead plants and animals being broken down by decomposers and returning to the soil. Nitrogen is recycled in nature, by: soil bacteria and fungi, acting as decomposers, converting proteins and urea into ammonia the conversion of this ammonia to nitrates by nitrifying bacteria the conversion of nitrates to nitrogen gas by denitrifying bacteria the fixing of nitrogen gas by nitrogen-fixing bacteria living in root nodules or in the soil or by the action of lightning.
D: Interdependence (Higher in bold) Competition may influence the distribution and population size of animals or plants, organisms may compete for water, shelter, light and minerals. Similar animals in the same habitat will be in close competition for the same resources. Organisms within a species compete in order to survive and breed. Interspecific competition occurs between organisms of different species e.g. red and grey squirrels compete for the same food. Intraspecific competition occurs between groups of organisms of the same species. This type of competition is often more significant because the needs of the two groups are identical. An ecological niche is the role of an organism, this includes food, shelter, when they are active etc. Similar organisms will occupy similar ecological niches, like red and grey squirrels. The size of a predator population will affect the numbers of prey and vice versa The populations of some predators and their prey show cyclical fluctuations in numbers. The cycles of population for predator and prey are out of phase with each other because it takes a while for one population to respond to the changes in the other population. Some organisms benefit from the presence of organisms of a different species. An example of such a relationship is a cleaner species, like the oxpecker bird that eats ticks and fleas from the skin of the buffalo. Other types of interdependence between organisms are: parasitism, where the parasite benefits to the living host s detriment, including fleas and tapeworms mutualism, where both species benefit including cleaner species and pollination by insects. The interdependence of organisms determines their distribution and abundance. Nitrogen-fixing bacteria in the root nodules of leguminous plants are an example of mutualism.
E: Adaptations (Higher in bold) Animals and plants that are adapted to their habitats are better able to compete for limited resources. Adaptations to cold environments help organisms survive: anatomical methods of reducing heat loss, including insulation (thick coats and blubber) and small surface area compared to volume behavioural adaptations, including migration to warmer climates and hibernation to save energy. Adaptations to hot environments help organisms survive: behavioural and anatomical methods of increasing heat loss, such as storing fat in one area, having large ears and a large surface area to volume ratio to lose more heat behavioural methods of reducing heat gain like resting in the shade, bathing in water and being active at night when it is cooler. Adaptations to dry environments help organisms survive: behavioural (spend time underground where it is moist), anatomical (small surface area to volume ratio to reduce water loss) and physiological (produce little sweat and urine to conserve water) methods for coping with lack of water. Counter-current heat exchange systems (eg in penguins) minimise heat loss. Some organisms are biochemically adapted to extreme conditions, including different optimum temperature for enzymes in extremophiles and organisms with antifreeze proteins. Features of successful predators include: binocular vision to judge distance and size hunting strategy breeding strategy. Some animals are adapted to avoid being caught as prey: eyes on side of head for wide field of view; living in groups (herds or shoals) to reduce the chance of being caught cryptic and warning colouration mimicry breeding strategy (synchronous breeding). Some organisms are specialists, they are well adapted to only certain habitats. Some species are generalists, they can live in a wide range of habiats but can easily be outcompeted.
F: Natural selection (Higher in bold) There are variations within a population of organisms of the same species. Animals and plants that are better adapted to their environment are more likely to survive. Over long periods of time, groups of organisms can change and that this is called evolution. When environments change, some animal and plant species survive or evolve but many become extinct. Darwin s theory of evolution by natural selection includes: presence of natural variation competition for limited resources 'survival of the fittest' inheritance of 'successful' adaptations. Adaptations are controlled by genes and that these genes can be passed on to the next generation. Over long periods of time the changes brought about by natural selection may result in the formation of new species. Speciation requires geographical or reproductive isolation of populations because they must not be able to breed and they will become adapted to the different conditions. Over time: many theories have been put forward to explain how evolution may occur most scientists accept the theory of natural selection first put forward by Charles Darwin. The reasons why the theory of evolution by natural selection met with an initially hostile response were that most people based their ideas on the bible. Natural selection as a theory is now widely accepted: because it explains a wide range of observations has been discussed and tested by a wide range of scientists. Lamarck s idea of evolution by the inheritance of acquired characteristics was different from Darwin s theory. Lamarck s theory was discredited: acquired characteristics do not have a genetic basis. The theory of natural selection has developed as new discoveries have been made, like the knowledge of genes and inheritance.
G: Population and pollution (Higher in bold) The human population is increasing exponentially. Population growth is the result of the birth rate exceeding the death rate The human population uses resources, some of which are finite, including: fossil fuels and minerals. As the human population increases, resource use increases and therefore more pollution is created; household waste sewage sulfur dioxide from burning fossil fuels carbon dioxide from burning fossil fuels. The developed countries of the world, with a small proportion of the world s population, have the greatest impact on the use of resources and the creation of pollution. The term carbon footprint is the amount of greenhouse gases given off in a certain period of time. The causes and consequences of: global warming is caused by greenhouse gases such as CO 2 and causes the earth s atmosphere warm up ozone in the atmosphere is destroyed by CFCs, this allows harmful UV radiation through, which can cause skin cancer acid rain is caused by sulphur dioxide and nitrogen oxides which come from the combustion of fossil fuels, it damages plants, acidifies lakes and caused bronchitis. Pollution can affect the number and type of organisms that can survive in a particular place. The presence/absence of indicator species helps to indicate the level of pollution, including: water pollution waterlouse, sludgeworm, rat-tailed maggot and mayfly larva air pollution lichen. Pollution can be measured: by direct measurement of pollutant levels by measuring the occurrence of indicator species. The advantages of using living things to measure pollution are it is quick, easy and cheap. The disadvantages of using living things to measure pollution are it is not always reliable. The advantages of using non-living methods to measure pollution are it is reliable and gives numerical data which is easy to compare. The disadvantages of using non-living methods to measure pollution are it often requires expensive equipment and specially trained staff.
H: Sustainability (Higher in bold) Organisms like whales, become extinct or endangered, because of: climate change habitat destruction hunting pollution competition. Endangered species can be conserved, by: protecting habitats legal protection education programmes captive breeding programmes seed banks creating artificial ecosystems. The reasons for conservation programmes, include: protecting human food supply ensuring minimal damage to food chains future identification of plants for medical purposes cultural aspects. Species are at risk of extinction if the number of individuals or habitats falls below a critical level because there isn t enough genetic variation in the population and the populations may be restricted to small areas. Species are at risk of extinction if there is not enough genetic variation in the population because the species will be less likely to adapt to changes in the environment or a new disease. A conservation programme should ensure: that the genetic variation of key species is large enough to cope with changes the populations are viable, which means that there are enough individuals to reproduce without inbreeding there are plenty of available habitats that species can interact with other species A whale species distribution depends on their feeding habitats. Both living and dead whales have commercial value: tourism when alive; food, oil and cosmetics when dead. There are issues arising from keeping whales in captivity: entertainment, research, captive breeding programmes and lack of freedom. Some aspects of whale biology are still not fully understood: communication, migration patterns and survival at extreme depths. It is difficult to prevent whaling, because of: getting international agreement, policing and enforcing such agreements and hunting for research.