Ecology (part 1) - Biotic and Abiotic Factors

1. Chapter 21

2. Lesson Objectives At the end of the lesson, you should be able to (a) briefly describe the non-cyclical nature of energy flow (b) explain the terms producer, consumer and trophic level in the context of food chains and food webs (c) explain how energy losses occur along food chains, and discuss the efficiency of energy transfer between trophic levels

3. Definition: • Ecology: the study of interactions between organisms and the physical and chemical factors making up their external environment • Ecologists study both the i) biotic (living environment) – consists of all the living things that an organism interacts with ii) abiotic (non-living environment) - consists of physical factors e.g. light, water, pH of soil or water

4. Terms to be familiar with Habitat: the place where an organism lives in Population: a group of organisms of the same species living in a particular habitat Community: All the population of organisms living in a particular habitat Ecosystem: is made up of a community and its physical/ abiotic environment Biomes: distinct ecological communities of plants and animals living together in a particular climate

6. The World’s Major Land Biomes Temperate grassland Tropical rain forest Temperate forest Tundra Northwestern coniferous forest Mountains and ice caps Tropical dry forest Desert Temperate woodland and shrubland Tropical savanna Boreal forest (Taiga)

7. Abiotic and Biotic Factors Abiotic Factors Biotic Factors - the living components of the environment, such as plants, animals and fungi, that affect ecological functions. ECOSYSTEM - non living components of an ecosystem e.g. sunlight

8. Habitat: Mangrove swamp Biotic environment Plants • Mangrove trees, etc Animals • mud skippers • sand flies • monitor lizards • crabs

9. Abiotic environment 1. Salinity of sea water 2. pH 3. Temperature 4. Amt. of dissolved O2in mud 5. Amt. of light available 6. Amt. of nutrients

10. The Physical Environment

11. The Physical Environment • Occurrence and distribution of plants and animals are determined by i) climatic (e.g. amt. of light, water, temperature) & ii) topographical factors (physiogeographic characteristics of land in terms of elevation, slope, and orientation)

12. 1) Light Why do some plants climb? • Light intensity greater • A factor that affects distribution and growth of plants & animals • Plants have adaptations to enable them to climb

13. 2) Temperature • Varies with seasonal changes • Affects physiological activities of plants and animals (because enzymatic reactions affected) Adaptations of some flowering plants: 1.Underground storage organs 2.Shedding of leaves 3.Forming seeds that are resistant to heat, drought or cold just before the seasons arrive

14. 3) Water Adaptations of xerophytes to dry climate: 1. shed leaves (reduce transpiration) 2. fleshy stems (store water) 3. green stems (able to photosynthesize) Xerophytes: plants which can live in conditions of prolonged drought in their habitat

15. Other xerophytes…

16. Marram grass • a species of perennial grass • used to prevent or stop erosion of dunes • sand-binder and dune-builder • has shallow roots and a coarse, stiff structure

17. T.S. of marram grass leaf Adaptations of marram grass 1) Sunken stomata that lie in grooves on the upper surface 2) Spines (tiny hairs) - discourage browsing animals - trap water vapour diffusing out of the stomata (increases humidity around the stomata and reduces rate of transpiration) 3) Leaves roll up (reduces s.a exposed to surroundings when the leaves lose too much water)

18. Casuarina Water loss reduced through • Leaves reduced to tiny sheaths at nodes • Photosynthesis by long green stems whose stomata lie in grooves protected by minute hair

19. Hydrophytes 3 types 1) Completely submerged e.g. hydrilla 2) Partially submerged e.g. water lily 3) Free floating e.g water hyacinth

20. Hydrophytes (completely submerged) hydrilla fanwort

21. Hydrophytes (partially submerged) Cattail (Typha latifolia) Water lilies

22. Hydrophytes (free floating) duckweed water hyacinth

23. Adaptations of hydrophytes The presence of little or no mechanical strengthening tissue in stems and leaf petioles. They are normally supported by water all around them and so have no need of mechanical strengthening. Lack the external protective tissues e.g. cuticle required by land plants to limit water loss Have very specialized leaf shapes (often highly dissected or divided); creates a very large surface area for absorption and photosynthesis Roots are reduced and main function is anchorage Air-filled cavities often extend throughout the leaves and stems of aquatic plants, providing an internal atmosphere http://www.countrysideinfo.co.uk/wetland_survey/adaptns.htm 1. 2. 3. 4. 5.

24. Mangroves

25. Pneumatophores

26. 4) Oxygen • Aerobic organisms possess special adaptations for obtaining sufficient O2for respiration • e.g. pneumatophores of mangrove (enable mangrove plants to breathe in O2-poor mud) • Fish are usually air breathers i.e. they come to the water surface to gulp air

27. 5) Salinity Freshwater Seawater high water potential Low water potential H2O H2O H2O H2O H2O H2O Gain water by osmosis Lose water by osmosis

28. Problems faced by freshwater fish: 1. excess water entering body cells 2. salt loss from cells Problems faced by marine fish: Water loss from cells Salts moving into cells from seawater

29. Adaptations of marine fish 1. Saltwater fish have slimy scaly skin (reduces rate of water loss) 2. Secretion of salts into surroundings by cells in the gills 3. Kidney excretes salts and small amts. of water, producing highly concentrated urine Adaptations of freshwater fish 1. Uptake of salts by cells in the gills 2. Kidney reabsorbs salts and produces large amts. of dilute urine

30. 6) pH (of soil/water) ▪ Refers to the acidity or alkalinity of a solution ▪ Changes in pH do occur especially if the pH of water depends on the amt. of hydrogen carbonates/ bicarbonates present in the water ▪ During the day Photosynthetic activity of the plants uses up the CO2in the water, making the water alkaline ▪ During the night Photosynthesis ceases and the CO2produced as a result of respiration makes the water more acidic