[BIO] Chapter 19 - Ecology

© Hee Xin Wei (Copyrighted) Topic 19: Organisms and their Environment

Chapter Analysis FOCUS EXAM WEIGHTAGE •Highest weightage •Constitute to around 17% in Paper 2 in the past 5 years •Tested every year •tested thrice in section B in the past 5 years •Straightforward chapter •content heavy, memorisation intensive

food chain carbon cycle Key Concept © Hee Xin Wei (Copyrighted)

ecosystem Ecology is the study of interactions between organisms and the interactions between these organisms and their environment Ecosystem consists of a community and the abiotic environment / physical environment. -Community is all the organisms that live in a particular habitat, thus these populations of organisms interact with one another. -Abiotic environment is the physical factors in the environment that the community interacts with such as pH of water and soilaffect enzyme activity Temperature affect enzyme activity and metabolism of organisms Light Intensity affect rate of photosynthesis Water availability water is important for the survival of all living things Oxygen content necessary for aerobic respiration Salinity of water and soil affect water potential of environment thus water uptake or removal for plants © Hee Xin Wei (Copyrighted)

food chain Food chain -A food chain is a sequence of energy transferred in the form of food, between organisms in an ecosystem. -Each level of the food chain is known as trophic level -Interconnected food chains form a food web Producer: -organisms that contain chlorophyll thus are able to convert light energy from the sun to chemical energy thus making their own food via photosynthesis -provides food for other organisms in the community thus occupies first trophic level in food chain Consumer -Organisms that are not able to make their own food and obtain energy by feeding on other organisms -Primary consumers feed on primary producers directly. They are herbivores. -Secondary consumers feed on primary consumers. They are carnivores. -Tertiary consumers feed on secondary consumers. They are carnivores. Food Web - Food web consists of two or more food chains linked together. © Hee Xin Wei (Copyrighted)

Non-cyclic energy flow 1)In any ecosystem, the ultimate source of energy is the Sun. Light energy from the sun is absorbed by chlorophyll in producers and converted into chemical energy during photosynthesis 2)Plants make its own food via photosynthesis and contain carbon in the form glucose, sucrose, starch. 3)Energy is passed from one trophic level to another when primary consumer feed on the producers and so on. 4)Organisms at each trophic level pass on about 10% energy to the next trophic level compared to what they receive. 5)This is because energy is lost at every trophic level as heat in respiration, uneaten organism parts and through excreted and egested waste material. These energy lost cannot be recycled. 6)Faeces, excretory products and dead organisms contain trapped chemical energy. This energy is released through the activity of decomposers. Decomposers use some of this trapped chemical energy for their needs, releasing CO2. The rest of the energy is lost as heat. © Hee Xin Wei (Copyrighted)

pyramid of food chain pyramid of number -A pyramid of numbers shows the relative population of each trophic level in a food chain at a particular time -Pattern: Usually, the number of producer at the base is highest number, as it is needed to feed the next level. The number of consumers gradually decreases towards the top -Disadvantage: It is not an accurate estimate of the amount of energy at each trophic level because the population number does not always correspond to the amount of energy it can transfer to the next trophic level, e.g. a single tree can support a large population of caterpillars © Hee Xin Wei (Copyrighted)

pyramid of food chain pyramid of biomass -A pyramid of biomass shows the dry mass of organisms at each trophic level in a food chain. -Pattern: The biomass of the producer is the largest as it supplies all the energy for the resumers. Biomass is lost along the food chain due to loss of energy thus biomass decreases along the food chain. -Disadvantages: Dry mass cannot be easily obtained from every animal e.g. human being, large animals like tiger It is also destructive as it involves drying the organism at 100 °C, which will affect the food chain/ food web © Hee Xin Wei (Copyrighted) One single tree has larger biomass than a large number of caterpillar.

carbon cycle Removal of carbon dioxide 1.Plants convert atmospheric carbon dioxide into glucose during photosynthesis. Glucose can be converted to other carbohydrates, proteins and fats within the plants Return of carbon dioxide 2.Carbon dioxide is returned to the atmosphere when cellular respiration takes place in living organisms. 3.When the plants and animals die, decomposers such as bacteria and fungi break down the organic matter into carbon dioxide, which is released back to the atmosphere 4.Fossil fuels are formed from the fossilised remains of dead plants and animals. Carbon compounds from these dead organisms are stored as fossil fuels. 5.When fossil fuels and wood are burnt, carbon dioxide is produced. Importance of carbon cycle -Ensures that there is a continuous supply of carbon dioxide for plants to carry out photosynthesis. -Allows photosynthesis to convert light energy from the Sun into chemical energy in food, which non-photosynthetic organisms can feed on to stay alive. -Enables energy to flow through the ecosystem. Carbon compounds carry the stored energy from organism to organism in the food chains of an ecosystem. -Maintains the correct concentration of carbon dioxide in the atmosphere. © Hee Xin Wei (Copyrighted)

carbon sinks An area that that absorbs more carbon than it releases as carbon dioxide Oceans •Atmospheric carbon dioxide is absorbed by the ocean as carbon dioxide dissolves in the ocean’s water •Dissolved CO2 is used by phytoplankton and algae in photosynthesis. •Iron compounds increases the photosynthetic activity of phytoplankton. •The organisms in the oceans store carbon compound. When they die, they may sink and be buried deep in the seabed and may form fossil fuels. Forests •The plants in forests absorb atmospheric carbon dioxide for photosynthesis •A large amount of carbon compound is stored in trees. When trees die, they are buried deep in the ground and form coal, a kind of fossil fuels. © Hee Xin Wei (Copyrighted)