Ecosystems

1. Ecosystems Science 10

2. Biosphere • This is the title given to the area of the earth where life exists. • It is about 20km thick, from the bottom of the oceans to the highest point in the atmosphere where life can be found. • The biosphere can be divided into biomes.

3. Biomes • These are divided according to the type of vegetation which can be found in its midst. • There are three main types: • Terrestrial • Freshwater • Marine • Each of these biomes can be divided into a wide variety of ecosystems.

4. Ecosystems • This includes all the organisms in an area that interact with each other and with their environment. • The fuel for ecosystems is the sun. • Sunlight is captured by green plants for photosynthesis and stored as carbohydrate energy. • This energy then gets passed on as herbivores eat plants and carnivores eat the herbivores.

5. Two main factors in an ecosystem • Abiotic factors- these are all of the nonliving aspects of the ecosystem that affects the organism. • These include water, carbon dioxide, minerals, light, temperature, wind, space, etc… • Biotic factors- these are all of the living organisms in an ecosystem

6. Modes of Nutrition • Autotrophs • Capture sunlight or chemical energy • Producers • Heterotrophs • Extract energy from other organisms or organic wastes • Consumers, decomposers, detritivores

7. Simple Ecosystem Model energy input from sun PHOTOAUTOTROPHS (plants, other producers) nutrient cycling HETEROTROPHS (consumers, decomposers) energy output (mainly heat)

8. SPRING Consumers • Herbivores • Carnivores • Parasites • Omnivores • Decomposers • Detritivores fruits insects rodents, rabbits birds SUMMER fruits rodents, rabbits insects birds Seasonal variation in the diet of an omnivore (red fox)

9. Does one ecosystem hold more energy than another? • How is energy stored and transferred within an ecosystem? • How does it leave an ecosystem?

10. These types of questions are important because the energy that is captured by plants through photosynthesis determines the amount of energy that is available for all other organisms in the ecosystem. • Human survival depends on the amount of energy that is stored in agricultural ecosystems

11. Compared with animals, green plants produce more energy per unit land area. (see results from graph exercise) • Thus, most of the energy in an agricultural ecosystem is found in the crops, such as the field of corn. • Only a portion of this energy is transferred to livestock that eat the plants. • As a result, animals and animal products contain less energy than plant and plant products that are raised on the same amount of land.

12. This begs the question; Why is only some of the original energy transferred to the plant eaters? • What happens to it? • Why is some lost from level to level?

13. Trophic Levels • Ecosystems can be thought of as being made up of several feeding levels, or Trophic levels • All the organisms at a trophic level are the same number of steps away from the energy input into the system

14. Trophic Levels • Producers (autotrophs) make up the first trophic level. • Primary consumers (heterotrophs) feed at the second trophic level. • Secondary consumers (heterotrophs) feed at the third trophic level and so on. • All the organisms at a trophic level are the same number of steps away from the energy input into the system

15. Most of the energy that enters each trophic level is used by the organisms at this level just to stay alive. • The organisms need energy to move from place to place, grow, reproduce, and carry out other activities. • Some of the energy cannot be used and passes out of the organisms as waste. • Only a small percentage of the energy remains stored in each organism as body tissues. • It is this energy that is available as potential food for consumers in the next trophic level.

16. Food Chain MARSH HAWK • A straight line sequence of who eats whom • Simple food chains are rare in nature UPLAND SANDPIPER GARTER SNAKE CUTWORM

17. FoodWeb Many organisms eat a variety of foods and consume organisms from many different trophic levels. The complex relationship is demonstrated via a food web.

18. Decomposer Food Chains • Organisms that receive energy from dead plant and animal material • Make up majority of food chains • Scavengers eat the remaining energy in large dead organisms • Ex: Vultures eat the carcasses of dead animals • Decomposers – types of organisms that break down cells to extract remaining energy • Ex: fungi and bacteria

19. Grazing Food Web Detrital Food Web Two Types of Food Webs Producers (photosynthesizers) Producers (photosynthesizers) decomposers herbivores carnivores detritivores decomposers ENERGY OUTPUT ENERGY OUTPUT

20. Primary Productivity • Gross primary productivity is ecosystem’s total rate of photosynthesis • Net primary productivity is rate at which producers store energy in tissues in excess of their aerobic respiration

21. Primary Productivity Varies • Seasonal variation • Variation by habitat • The harsher the environment, the slower plant growth, the lower the primary productivity

22. Pyramids • Pyramid of Numbers – shows how the greatest number of organisms is in the first trophic level, least number on top of the trophic level • Pyramid of Biomass –shows the relative mass of the organisms at each trophic level • Pyramid of Energy Flow – shows how the energy available at each trophic level is greatest at the bottom of the food chain and least at the top

23. Pyramid of Biomass • Aquatic ecosystem in Florida • Site of a long-term study of a grazing food web third-level carnivores (gar, large-mouth bass) Biomasspyramid 1.5 second-level consumers (fishes, invertebrates) 1.1 first-level consumers (herbivorous fishes, turtles, invertebrates) 37 decomposers, detritivores (bacteria, crayfish) primary producers (algae, eelgrass, rooted plants) 809 5

24. Pyramid of Energy Flow • Primary producers trapped about 1.2 percent of the solar energy that entered the ecosystem • About 10% passed on to next level top carnivores 21 carnivores decomposers detritivores 383 herbivores 3,368 producers 20,810 kilocalories/square meter/year

25. All Heat in the End • At each trophic level, the bulk of the energy received from the previous level is used in metabolism • This energy is released as heat energy and lost to the ecosystem • Eventually, all energy is released as heat

26. Work on questions 1-4 page 274 • Work on questions 5-10 pages 275-276. • Complete “Going with the Flow” worksheet

27. Feeding levels • First trophic level – always plants • Second trophic level – primary consumers • Third trophic level – secondary consumers • Energy flows through the food chain but only about 10% of the energy is passed on from one trophic level to the next. • Ex: Plant has 100kJ, caterpillar uses 10% for life processes, 90% is lost as heat or waste

28. Carrying Capacity • Can any population of organisms keep growing forever? What might limit its numbers? • The largest number of individuals in a species that an environment can support is called the carrying capacity. • 4 factors that determine carrying capacity • Materials/energy –limited by the amount of usable energy, water, carbon • Food Chains- population sizes at each trophic level (predators, herbivores) • Competition – Intraspecific (same species)/Interspecific (between species) • Density – how many organisms occupy a given space at a given time

29. Factors which can limit the growth of a population include: • predation • shortage of food • disease • lack of water • lack of space

30. Factors That Affect the Size of a Population • Density Dependent: (overcrowding,) • If population density increases it can cause a decrease in the population • Increased stress = spread of disease and parasites • Increased aggression = neglect of offspring • These factors decrease the population numbers • Density Independent • Events that can decrease population numbers that are not dependent on the size of the population (ie. Forest fire)

31. Please work on questions 1-4 page 290 • Finish for homework