[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 or