Ecosystems Topic 1 : Using Energy

EcosystemsTopic 1: Using Energy Part of the Local Ecosystems Module Spotlight Biology Preliminary Text Chapter 4 Authors: D. Heffernan, J. Bastina, B. Grieve, K. Humphreys, A. Sartor Science Press 2002

Outcomes By the end of this module you should be able to: • Describe the flow of energy and matter in an ecosystem • Explain the roles of photosynthesis and respiration in ecosystems • List the uses of energy in organisms • Explain the role of decomposers in ecosystems • Explain how each local aquatic or terrestrial ecosystem is unique • Describe how producers, consumers and decomposers are related by using food chains and food webs

Outcomes Continued • Explain trophic interactions between organisms in the local ecosystem • Describe the importance of the cycling of materials in ecosystems • Describe the water, carbon-oxygen and nitrogen cycles • Explain the relationship between pollution and contamination by unwanted substances • Compare the energy flow and cycling of matter through disturbed and undisturbed ecosystems

Outcomes Continued You should also be able to: • Construct diagrams from electron micrographs of mitochondrion and describe its features • Construct food chains and food webs • Analyse tropic levels in ecosystems • Predict rates of human population growth

Using Energy Plants share an ability vital to life on Earth: they can use light to convert the simple, inorganic compounds from soil and air into the complex molecules they need. For this reason they are called autotrophs (auto: self, troph: food). Autotrophs make their own food. scenicreflections.com

Using Energy They are also called primary producers because they are the first producers of complex compound. Many living things cannot make their own food and therefore depend directly or indirectly on these primary producers for energy.

Using Energy Heterotrophs (hetero: other, troph: feeding) can store energy by synthesising and accumulating a variety of complex molecules, such as fats, oils and proteins, but they must obtain that energy by eating energy rich molecules contained in other organisms. animals.about.com

Using Energy Heterotrophs obtain the energy they need in many ways, most of which can be divided into three main strategies: • Eating plants (herbivores) • Eating Animals (carnivores) • Decomposing the remains of organisms and their waste (decomposers) hoax-slayer.com

Herbivores Herbiores (herb: plant): such as rabbits and kangaroos, eat plants that have stored energy in the form of sugars, starches and other complex carbohydrates. Because they are the first organisms to consume the energy and carbon that is fixed by primary producers, herbivores are also called primary consumers. hoax-slayer.com

Herbivores Plants store much of their energy in the form of a polysaccharide called starch. Many other orgnaisms, including us humans can break the chemical bonds in starch (a type of carbohydrate) very easily so it serves as an excellent source of food. web.visionlearning.com

Herbivores A lot of plants use another carbohydrate called cellulose to build tough, flexible cells walls to support and protect their cells. In larger plants this cellulose forms the basis of wood. Can you tell the difference between the two molecules? rsc.org

Herbivores Lets have another look at the two molecules:

Herbivores Cellulose is very similar to starch but the type of chemical bond between glucose molecules in cellulose makes it very difficult for other organisms to digest. These bonds can only be broken by the enzyme cellulase, however most animals cannot manufacture it. Only a few snails, clams and a few species of microbes produce cellulose and can digest cellulose. animals.about.com

Herbivores Think about this: • Do you think the fact that the cellulose bond is so difficult to break is a benefit to large plants like trees? Why/why not? savingourtrees.wordpress.com

Leaf Eaters The most familiar plant eaters such as cattle and sheep, are grazers. They feed on the leaves of grasses. To help them extract as much energy as possible from their food, grazing animals depend on a variety of adaptations that involve feeding behaviour and the design of their digestive organs. pitneyfarmshop.co.uk

Leaf Eaters Grazers chew leaves into a pulp with powerful molars. When the pulp is swallowed, it enters a long and complex digestive tract where cellulose is broken apart with the help of beneficial microbes (mutualism). d91.k12.id.us

Leaf Eaters Grazers don’t extract very much energy from a mouthful of food so they spend most of their time eating! Herbivores that eat the leaves of trees often have even more trouble getting enough energy. free-extras.com

Leaf Eaters Some koalas that eat only leaves from a certain species of eucalypt sometimes live on the edge of starvation. They sleep for extended periods of time to conserve energy. Cool fact: baby koalas are fed some of its mothers faeces to that is will obtain the microbes needed to digest its food. virtualoceania.net

Seed, Fruit and Berry Eaters Many other herbivores feed on seeds and fruit. Some, such as finches, specialise in eating seeds of a particular size and type. Other like cockatoos use their long, sharp beaks to break hard seeds and fruit open. ozfolksongaday.blogspot.com

Seed, Fruit and Berry Eaters We also depend heavily on seeds and fruit as food. Most of the worlds population live on seeds of a single plant family. The grasses which include rice, corn, wheat, oats and barley en.wikipedia.org

Homework • Contrast herbivores with carnivores • When cows chew their cud, they regurgitate food from their stomach and rechew it. How would this help them?

Ecosystems Topic 1 : Using Energy