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Biology Unit 3: Ecology UNIT 3 – TOPIC 1 Biodiversity Recognise that biodiversity includes the diversity of species and ecosystems Biodiversity is the variety of species and ecosystems. An increased level of biodiv...

Biology Unit 3: Ecology UNIT 3 – TOPIC 1 Biodiversity Recognise that biodiversity includes the diversity of species and ecosystems Biodiversity is the variety of species and ecosystems. An increased level of biodiversity is important in enabling an ecosystem to better adapt to change. There are three types of biodiversity. 1. Genetic Diversity - The number of different alleles possessed by a species. - If a change to the allele frequency or gene code occurs, a smaller proportion is affected if there are many more alleles compared to only a small amount. 2. Species Diversity - The number of different species at a particular time in a particular ecosystem - If there are more species, a change is likely to only affect a small proportion of them rather than the entire or half the population due to different niches and adaptations of abiotic factors. 3. Ecosystem Diversity - The number of different ecosystems or biomes and the variation between them Determine diversity of species using measures such as species richness, evenness (relative species abundance), percentage cover, percentage frequency and Simpson’s diversity index Ecology is the study of plants and animals in relation to their total environment. This environment is the sum of all abiotic and biotic factors which affect growth and survival. Abiotic Factors: Non-living factors (e.g., salinity and pH of soil, oxygen percentage, temperature etc.) Biotic Factors: Living factors (interactions with other organisms, predator-prey relationships, competition, symbiosis) Ecologists study these interactions at various levels of ecological complexity. Individuals, Populations, Communities, Entire ecosystems Measures of diversity is usually based on distribution and abundance. Distribution – Where a species is found. Abundance – How many of a species there is Quadrats and transects are the basis of ecological sampling. Quadrats – The area marked out with a frame for the purpose of gathering data related to populations of organisms in each area. - Usually, 1m2 but can be adapted to suit the specific ecosystem. - Organisms inside the quadrat are counted and recorded. - Several quadrats placed randomly around a habit can provide information regarding abundance and density of species (useful for percentage frequency) Transects – Line marked out randomly through a habitat. - Every organism on the line at regular intervals or within the transect is recorded. - Variations in community composition and abiotic gradients can be assessed. - There are two types of transects: a) Line Transects are time efficient and can minimise disturbance to environment however not as precise (only really measures distribution) b) Belt Transects extend out a specific distance to either side of the line and provide accurate estimations of distribution and abundance. To study these things various measures are used. 1) Species Richness: The number of different species in an ecosystem (only informs about distribution) 2) Species Evenness (relative abundance): Tells you how many of a species there is in relation to the total number of individuals. 3) Simpson’s Diversity Index (SDI): Measures the probability that two randomly selected organisms are from different species (higher SDI means a higher biodiversity) Σ𝑛(𝑛−1) - Formula 𝑆𝐷𝐼 = 1 − ( ) 𝑁(𝑁−1) - Closer to 1 means higher biodiversity, more complex food webs and environmental change is less likely to have damaging effects on the ecosystem as a whole 4) Percentage Frequency: Used to determine how many quadrats a species is present in 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑞𝑢𝑎𝑑𝑟𝑎𝑡𝑠 𝑤𝑖𝑡ℎ 𝑠𝑝𝑒𝑐𝑖𝑒𝑠 - %𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 = 𝑡𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑞𝑢𝑎𝑑𝑟𝑎𝑡𝑠 ∗ 100% - Can be used when the area is large. 5) Percentage Cover: The percentage of a given area covered by a particular organism (usually plants) - Useful for large numbers of individuals 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑞𝑢𝑎𝑑𝑟𝑎𝑡𝑠 𝑤𝑖𝑡ℎ 𝑠𝑝𝑒𝑐𝑖𝑒𝑠 - %𝐶𝑜𝑣𝑒𝑟 = ∗ 100% 𝑡𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑞𝑢𝑎𝑑𝑟𝑎𝑡𝑠 - This can measure the following. a) Canopy Cover → Measures total area covered by the plant b) Ground Cover → Area of soil covered by plants, rocks, and plant litter Menhinick Index: 𝑠 𝐷= √𝑁 𝐷 = 𝑠𝑝𝑒𝑐𝑖𝑒𝑠 𝑑𝑖𝑣𝑒𝑟𝑠𝑖𝑡𝑦, 𝑠 = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑡 𝑠𝑝𝑒𝑐𝑖𝑒𝑠, 𝑁 = 𝑡𝑜𝑡𝑎𝑙 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠 Use species diversity indices, species interactions (predation, competition, symbiosis, disease) and abiotic factors (climate, substrate, size/depth of area) to compare ecosystems across spatial and temporal scales Temporal Scale: considers an ecosystem over a particular timeframe. Hours to days, seasonal, years Spatial Scale: size of ecosystem being considered. Population density refers to how many individuals there are per unit area/volume. In addition to using the quantitative species diversity indices, we can compare ecosystems using biotic and abiotic relationships. Biotic factors include. Predation → one species kills and eats another - Within a given amount of space, there is more prey, which means a greater likelihood that they can catch, kill, and eat this prey. - The prey population will hence suffer more deaths and we can compare the rates of predation between ecosystems or within the same ecosystem over time. - Usually, more prey than predators Competition → two or more species compete for the same resource - Species need to compete to get the best/most resources. - Each population of species needs resources however these are limited. - Interspecific Competition → competition between different species. - Intraspecific Competition → competition within the same species. Disease → pathogenic condition of a host that can be caused by a pathogen or parasite - Conversely, when a population is small, the disease may be transmitted at a weaker and slower rate. - When there are more individuals within an area (higher density), disease is more easily transmitted between individuals causing more harm/deaths.  Symbiosis is the long-term interaction between two species living in physical proximity. - Mutualism is when both species benefit from their interaction (e.g. grazing cattle and cattle egret birds that eat insects near cows and benefits cows as it removes annoying bugs) - Amensalism is when an interaction has a negative effect on one and no effect on the other. - Neutralism occurs when both species have no effect on each other. - Commensalism occurs when one is affected positively, and the other isn’t benefitted or harmed. Abiotic Factors Include Climate: almost all species are affected by climate, and hence we can compare ecosystems across different climates, or the same climate as the temperature, weather patterns, and other conditions change over time (particularly due to man-made climate change). Substrate: The surface or substance where organisms live (e.g., fresh or salt water) is analysed to provide us with information about the nutrients and composition of the environment which would let us estimate species found there. Size/Depth of Area: How much space an ecosystem occupies. - Important for deforestation, coral bleaching, and destructive events. Explain how environmental factors limit the distribution and abundance of species in an ecosystem. Environmental factors can limit the distribution and abundance of species in an ecosystem because every organism has a slightly different tolerance limit. A tolerance limit is the range of environmental conditions that an organism can survive in. o i.e. size of area, climate, soil structure, aquatic factors Classification processes Recognise that biological classification can be hierarchical and based on different levels of similarity of physical features, methods of reproduction and molecular sequences Classifying Organisms allows scientists to: Identify harmful or dangerous organisms. Recognise potentially beneficial organisms. Understand Relationships Manage information related to the vast biodiversity of organisms on the planet and understand interactions between them and humans particularly if a species is endangered. Understand evolutionary relationships. Morphological definition = difference in form and structure of organisms is used to divide them into species Biological definition = interbreeding natural populations that produce offspring Ecological definition = defines a species by the resources a particular group of organisms use The Linnean System Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species This method uses morphological features of organisms to create groups according to their similarities The naming of organisms is based on the Linnean system’s binomial system. - The first name is the genus, the second name is the species. - E.g., Macropus rufus Describe the classification systems for similarity of physical features (the Linnaean system) methods of reproduction (asexual, sexual — K and r selection) molecular sequences (molecular phylogeny — also called cladistics) Classification By Reproductive Methods Organisms can be divided into two smaller groups related to their reproductive measures. - K-strategists (capacity) - longer lifespan - low rate of reproduction - individuals mature slowly. - parents have care for offspring. - only a few offspring at a time - population controlled by factors such as competition/ predation. - r-strategists (growth rate) - short lifespan - high rate of reproduction - individuals mature quickly. - parents have little to no care for offspring. - tend to have high numbers of offspring at a time. - Population is controlled by factors such as climate events/ fires etc. Classification by Methods of Interaction Organisms interact with biotic and abiotic environments and can be classified based on these. These species’ interaction is important as they impact the structure and integrity of the ecosystems. The survival of one species is dependent on the other species which it interacts. Population sizes also influence other species. - E.g., a small population of prey cannot sustain a large population for predators. Species interactions include: - Predator-prey: members of one species hunt and consume individuals of another species. - Competition: Members of different species compete for resources such as food and shelter. - Symbiosis: Individuals from different species demonstrate a close approximation. - Disease: An impairment occurs in the normal functioning of an organism cause by pathogens or non-infectious factors. Phylogenetic Classification Based on the assumption that the more physically alike organisms are, the ore related they are. It is the consideration of morphological and molecular similarities between species to classify them. Phylogeny → the pattern of evolutionary relationships between organisms Define the term clade A group of organisms that consist of a common ancestor and all its lineal descendants Recall that common assumptions of cladistics include a common ancestry, bifurcation and physical change Common Assumptions of Cladistics Related species share a common ancestor. - All life arose on earth only once. - All life has been produced from the reproduction of existing organisms. A common ancestral species that has split into two (bifurcation) from an ancestral group and undergone gradual genetic change. - When a lineage splits, it divides into exactly two groups. - Also note that there are some situations that may violate this such as adaptive radiation (which is rare) Populations that have bifurcated from an ancestral group and undergone gradual genetic and physical change. Recognise the need for multiple definitions of species Multiple definitions of species are required because some species definitions/concepts cannot be applied to organisms that do not reproduce sexually. For example, many organisms reproduce asexually (producing clones), undergo parthenogenesis, or can transition between sexual and asexual. Identify one example of an interspecific hybrid that does not produce fertile offspring (e.g. Mule, equus mulus) example is the Liger (Panthera tigris x Panthera leo). From a male lion and female tiger. Understand that ecosystems are composed of varied habitats (microhabitat to ecoregion) Microhabitats are small, localised habitats within a larger habitat. Each microenvironment has slightly different characteristics giving it its own microclimate Many microclimates and microhabitats can be found within an ecosystem. An ecoregion is a large area that has a distinct geography and contains a collection of organisms which are distinct to the area next to it. Can be formed by a large habitat or a combination of habitats. This means that ecoregions differ based on climate, geophagy and organisms. Explain how the process of classifying ecosystems is an important step towards effective ecosystem management (consider old-growth forests, productive soils and coral reefs) Old Growth Forests Management: prescribed burning Productive Soils Management: reduce overgrazing, select appropriate land preparation. Coral Reefs Management: control and removal of exotic species, conservation and recreational use policies Classification allows us to monitor, document and communicate information about biodiversity, which can be used to monitor how old-growth forests recover after a disturbance. E.g., the progression from tall open woodland to a tall, closed forest. Classification can also be used to identify which parts of an area have similar species composition and abiotic factors This data can be used to inform effective management, as similar management principles would apply to old growth forests with similar species composition. Describe the process of stratified sampling Stratified Sampling 1. Purpose: estimating population, density, distribution, considers environmental gradients and profiles such as zonation and stratification 2. Site selection: further surveys (temporal changes) can be carried out 3. Choice of ecological techniques Quadrats: marked area where you survey the organisms present If used, consider size, amount used, and how they are placed. Data is then collected by density, frequency, percentage cover, scaling measure. Transects: sampling line used to investigate change over distance in an ecosystem. 4. Minimising bias a) The larger the number of quadrats sampled, the more representative the data. b) Using random number generators to select sites for sampling decreases any unwitting bias by field workers.  c) Applying counting protocols ensures consistent counting of individuals throughout the sample area. Ensuring equipment, such as data loggers, are correctly calibrated; poorly maintained equipment leads to unreliable data that fails to provide a true assessment UNIT 3 – TOPIC 2 - Functioning ecosystems Sequence and explain the transfer and transformation of solar energy into biomass as it flows through biotic components of an ecosystem, including - Converting light to chemical energy - Producing biomass and interacting with components of the carbon cycle Converting Light into Chemical Energy a) Energy flows through the community of an ecosystem in one direction. b) The original source is light from the sun. c) Primary produces harness the energy to make biomass. - Autotrophs harness the sun’s energy through photosynthesis. (carbon dioxide and water form glucose, water, and oxygen by using sunlight) - Producers that don’t undergo photosynthesises carbon containing molecules to construct complex chemical compounds via chemosynthesis. d) Heterotrophs (consumers) are unable to produce their own chemical/organic compounds thus rely on autotrophs for their energy. e) Energy contained within produces and consumers is ultimately passes onto decomposers that are responsible for the constant recycling of nutrients. Analyse and calculate energy transfer (food chains, webs and pyramids) and transformations within ecosystems, - Including loss of energy through radiation, reflection and absorption - Efficiencies of energy transfer from one trophic level to another - Biomass The productivity of plants is their contribution made to the biomass of an ecosystem. Biomass → The dry weight of a given species in an ecosystem. Primary Productivity → The rate at which primary producers convert light to chemical energy, increasing biomass. Gross Primary Productivity → The rate at which plants use solar energy to incorporate carbon into organic compounds. Net Primary Productivity → (of an ecosystem) The rate at which it accumulates biomass. 𝑛𝑒𝑡 𝑝𝑟𝑖𝑚𝑎𝑟𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 = 𝐺𝑟𝑜𝑠𝑠 𝑃𝑟𝑖𝑚𝑎𝑟𝑦 𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 − 𝑀𝑒𝑡𝑎𝑏𝑜𝑙𝑖𝑠𝑚 FOOD CHAINS Linear feeding relationships showing passage of energy and nutrients. Each food chain begins with a producer organism. Energy initially harness by producers in photosynthesis at the first level is passed along the food chain in order. FOOD WEBS Are networks of interconnected food chains showing how various organisms are park of many linking food chains within a community. A particular organism can be at different trophic levels. Ecosystems and food webs contain a keystone species. Play a critical role in maintaining the integrity of an ecosystem. Their removal destabilises the ecosystem and affects all other organisms. PYRAMIDS Organisms in ecosystems occupy trophic levels, depending on where they are in feeding relationships. a) Some of the energy harness by plants and passed onto consumers is used for growth, movement, and reproduction however not all energy is passed down. b) Only about 10% is carried on to next tropic level. c) Each trophic level has a smaller biomass than the previous one. Describe the transfer and transformation of matter as it cycles through ecosystems (water, carbon, and nitrogen) WATER CYCLE 1. Water evaporates from the ocean. 2. Water moves over land as atmospheric gas (water vapour) 3. Water precipitates and falls as rain or snow. 4. Small amounts of water are stored in glaciers, lakes, and the water table. 5. Water runs off land into waterways. 6. Rivers flow back into ocean. CARBON CYCLE 1. Carbon enters ecosystems through photosynthesis as carbon dioxide on land and hydrogen carbonate ions in water. 2. It is incorporated into plant tissue and biomass during photosynthesis. 3. Carbon is eaten by consumers and passed along the food chain. 4. Is released via respiration as carbon dioxide. 5. Is released as body tissue decomposes. 6. Carbon is then stores as coal, oil, and natural gas which is produced from fossilised decomposing organisms. Greenhouse Effect d) Deforestation and the burning of fossil fuels contribute to an increase is carbon dioxide levels in the atmosphere. e) CO2 absorbs heat and insulates Earth by preventing heat to escape. f) Contributes to global weather pattern changes. NITROGEN CYCLE 1. Nitrogen in the atmosphere cannot be utilised by most organisms. 2. Bacteria in the soil and in or on the rots of legumes ‘fix’ nitrogen - Ammonification: Nitrogen is fixed into ammonia - Nitrification: Ammonia is converted into nitrite and nitrate ions by other bacteria 3. Plants absorb the ammonia and nitrate ions from the soil can convert them into proteins 4. Animals obtain nitrogen from the plants and other animals. 5. Decomposers break down faeces and dead tissue returning nitrogen to the soil as ammonia. - Denitrification: Breaks ammonia down to release N2 into atmosphere via soil bacteria. Define ecological niche in terms of habitat, feeding relationships and interactions with other species An ecological niche is the role that a particular species occupies in an ecosystem. There are two types of niches: 1. Fundamental Niche: All the potential resources that a species can use in its environment and requires the absence of competition. 2. Realised Niche: Some habitats and resources are not available because competitors occupy them (this is what the species uses). Realised niches are narrower than fundamental niches, therefore the species occupies a narrower range of habitats than it would in the absence of competition. Understand the competitive exclusion principle Two species that have exactly the same niche cannot coexist in the same community. This leads either to the extinction of the weaker competitor or to an evolutionary or behavioural shift toward a different ecological niche. If two competing species co-exist in a stable environment, they do so because of differentiation of their niche. Define keystone species and understand the critical role they play in maintaining the structure of a community A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem function. Remove the keystone and the whole arch fails. - Remove a keystone species and the ecosystem is hugely impacted. Analyse data (from an Australian ecosystem) to identify a keystone species and predict the outcomes of removing the species from an ecosystem. Example: Sea Otters Sea otters are a keystone species that feed on sea urchins. When sea otters are present, the urchins are limited to small individuals, confined to crevices and deeper areas. a) This means that kelp forests are allowed to grow. b) Therefore, there is a huge increase of kelp when sea otters are present. Furthermore, due to the increased abundance of kelp, kelp-feeding species can thrive as with increased prey/food, there is an increase of predators to each such food. c) Since this target smaller fish who are prey to larger fish, there is also an increase of larger fish all due to the increased abundance of otters as a keystone species. Population ecology Carrying capacity: size of the population that can be supported indefinitely on the available resources and services of the ecosystem. When a population is BELOW its carrying capacity, it will INCREASE in size (birth exceeds deaths) When a population is ABOVE its carrying capacity, it will DECREASE in size (death exceeds births) Calculating Population Growth: 𝑀𝑛 𝑙𝑖𝑛𝑐𝑜𝑙𝑛 𝑖𝑛𝑑𝑒𝑥 = 𝑚 𝑀 = 𝑖𝑛𝑖𝑡𝑖𝑎𝑙𝑙𝑦 𝑐𝑎𝑢𝑔ℎ𝑡, 𝑛 = 𝑖𝑛𝑑𝑖𝑣𝑖𝑑𝑢𝑎𝑙𝑠 𝑐𝑎𝑢𝑔ℎ𝑡 𝑜𝑛 𝑠𝑒𝑐𝑜𝑛𝑑 𝑠𝑎𝑚𝑝𝑙𝑖𝑛𝑔, 𝑚 = 𝑟𝑒𝑐𝑎𝑢𝑔ℎ𝑡 𝑠𝑎𝑚𝑝𝑙𝑒𝑠 Exponential Growth (J curve) the growth of a population in an ideal, unlimited environment Species that have exponential growth includes those with short generation times and/or have large numbers of offsprings (e.g. bacteria, weeds, insects, cane toads, humans) The graph represents births and deaths only, where the birth rate is substantially higher than the death rate Logistics Growth (S curve) Population cannot be sustained as resources are used Equilibrium population that the ecosystem can support (carrying capacity) Environmental resistance = environmental conditions that limit a species population from growing out of control (i.e through competition, abiotic factors) Changing Ecosystems Succession = plants/ animals colonise an area and over time, are replaced by other more varied organisms Primary: plants grow where no plants have grown before with no soil present o Pioneer plants = plant capable of invading bare sites, take advantage of lack of competition and alter the environment to allow the colonisation of other species (e.g.  lichens secrete acid and stimulate weathering, allowing small particles to settle and form a thin layer of soil o Climax community = remain unchanged so long as the site is undisturbed Secondary: plants grow where there has been previous population that were destroyed (i.e. fire) Feature Start of Succession Climax Community Types of species present R-selected, small organisms K-selected, larger organisms growing fast slowly growing Biodiversity Low High Biomass Low High Biotic Interactions Simple interactions (food chain) Complex interactions (food webs) Abiotic Interactions Bare ground, poor soil, low Good quality soil, high level of nutrient levels and unstable. nutrients, stable. Human activity has reduced biodiversity and has an impact on the magnitude, duration, and speed of ecosystem change. Urbanisation Creates pollution from rubbish that is generated Uses a lot of energy and has a lot of wastage. Habitat Destruction The clearance of native vegetation is a significant threat to biodiversity and leads to habitat fragmentation. Habitat fragmentation = the process by which areas of a habitat are lost, resulting in a large continuous habitat being broken into smaller, isolated habitats. o Creates ecological islands that have lower genetic diversity (increased homozygosity) and a simplification of food webs. Land Clearing Clear forests, where biodiversity is accommodated, are replaced by crops to which affects many animals (nesting, shelter, food for insects, bird and animals) Land and Soil Degradation Soil is a non-renewable resource Hard hoofed animals (sheep, cows, goats, horses) will compact the soil when they graze, creating opportunities for invasive, shallow-rooted introduced plants (i.e. weeds) at the expense of the deep-rooted native grasses By adding fertilizers, components of the soil are changed and generally degrade, leading to non- productive soil and erosion. Salination Land clearing and irrigation of crops raises the water table and brings salt with it and kills plants. o Before clearing = most water is used where it falls. The system is in balance (deep roots) o After clearing = saline groundwater rises and is concentrated at the surface by evaporation. Vegetation growth is affected  o Later = accumulation of salt at the surface kills protective plant cover. The land is open to erosion. Salt reduces the concentration of water; water is extracted from the root through osmosis and kills the plants. When deep roots are removed, the water runs off and is collected in the water table causing it to rise bring salt along. Soil is then inhospitable to the plants, causing them to die, to which soil is no longer held and erosion occurs consequently. Monoculture The agricultural practice of growing a single crop or plant species over a wide area for a large number of consecutive years o If a disease is introduced in the area, they are easy to spread as there is no biodiversity and will destroy everything. Introduced Species Human activity transfer organisms into places where they previously did not exist o New species often have no predators, are better competitors than native species or may harm native species Biomagnification Any concentration of a toxin, such as a pesticide or lipophilic poison, in the tissues of organisms at successively higher levels in a food chain. o e.g. polychlorinated biphenyls, products/man-made chemicals containing C, H, and Cl o Buildup of toxins in a food chain, higher and higher levels Over-exploitation Harvested at a rate that is unstainable, given their natural rates of mortality and capacities for reproduction o Threatens global biodiversity o Results in extinction at the population level or even extinction of whole species