Ch. 4 Ecosystems. Biology I Loulousis

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1 Ch. 4 Ecosystems Biology I Loulousis

2 Objectives 1.) Define ecology, ecosystem, and succession 2.) Identify and distinguish between the levels of organization in ecology 3.)Distinguish between primary and secondary succession

3 KEY CONCEPT Ecology is the study of the relationships among organisms and their environment.

4 Interactions and Interdependence Ecologists study everything from single cells to the entire planet

5 Levels of Organization biosphere biome ecosystem community population Organism (Species)

6 Levels of Organization INDIVIDUAL ORGANISM Species: Group of similar organisms that can breed and produce fertile offspring

7 Levels of Organization POPULATION Groups of individuals that belong to the same species and live in the same area

8 Levels of Organization Communities Different populations that live together in a defined area

9 Levels of Organization Ecosystem all the living organisms (biotic) that live in a particular place, together with nonliving(abiotic) or physical environment

10 Levels of Organization Biome A group of ecosystems that have the same climate and similar dominant communities

11 Levels of Organization The largest house is the biosphere. BIOSPHERE = contains the combined portions of the planet in which all life exists (land, water, air, and atmosphere) 8 km above earth s surface; 11 km below surface of the ocean

12 Biosphere Biome Ecosystem Ecosystem Community Community Organism Population Population Organism

13 Terrestrial Biomes Two factors that determine biomes: Temperature and precipitation Grouped by latitude into 1. Tropical Tropical rain forests Savannas (tropical grasslands) Tropical Deserts 2. Temperate Temperate grasslands Temperate forests Temperate deserts 3. High latitude Taiga Tundra

14 Aquatic Ecosystems Organized into 1. Freshwater ecosystems 2. Wetlands link between land and fully aquatic habitats Moderate flooding 3. Estuaries Fresh water mixes with salt water from ocean 4. Marine ecosystems

15 4.1 What is an Ecosystem? We are part of the environment along with all of Earth s organisms Interwoven in a complex web of relationships Think of a computer If you remove a circuit from a computer, it can change or limit the interactions of the computer s overall operation Similarly, removing one species from our environment can have many consequences

16 Habitat where a organism lives or population of species live

17 Diverse Communities in Ecosystems Biodiversity variety of organisms, their genetic differences, and the communities in which they occur # of species living in a ecosystem The more biodiversity a community has, the more stable it is

18 Ecosystem Inhabitants Most ecosystems contain a few large animals and some smaller animals Ecosystems tend to have more plants than animals The most plentiful organism in any ecosystem are usually microscopic bacteria and protists

19 Ecosystem Boundaries Physical boundaries are not always obvious Depend on how ecosystem is being studied Could be a single rotting log if only interested in the fungi and insects living in log Often it is a field, forest, or lake (an isolated area) No location is ever truly isolated

20 Change in Ecosystems over time When a volcano forms a new island, a glacier recedes and exposes bare rock, or a fire burns all of the vegetation in an area, a new habitat is created Pioneer species 1 st organisms to live in a new habitat Typically small, fast-growing plants Make the ground more hospitable for other species

21 Change in Ecosystems If a major disruption strikes a community, such as the wipe out of many organisms, the ecosystem reacts in such a way that it is restored to equilibrium Return to original state

22 Succession Succession is the regular progression of species replacement Primary succession succession that occurs where life has not existed before Secondary succession succession in areas where there has been previous growth Initial conditions and chance play roles in the process of succession No two successions are alike

23 Primary succession- New organisms form takes place on bare rock

24 Primary succession- New bare rock comes from 2 sources: 1. volcanic lava flow cools and forms rock

25 Primary succession- New bare rock comes from 2 sources: 2. Glaciers retreat and expose rock

26 Pioneer organisms- the first organisms to live in new habitat Ex: lichens are the first to colonize lava rocks

27 Primary succession-

28 Secondary succession- sequence of community changes that takes place when a community is disrupted by natural disaster or human actions takes place on existing soil

29 Secondary succession- Ex: A fire levels portions of a forest

30 Secondary succession- Ex: A farmer plows his field

31 Secondary succession-

32 Pond Succession

33 Glacier Bay: Ex. Of Succession Receding glacier is good example of succession because land is continually being exposed as the face of the glacier moves back Glacier Bay receded 100 km (62 miles) over the last 200 years Seeds and spores of pioneer species carried in by wind Include lichens, mosses, fireweed, willows, cottonwoods» At first, grow close to ground hurt by mineral deficiency After 10 years, alder seeds come in and take root Added nitrogen allows willows and cottonwoods to grow with vigor After 30 years, dense thickets of alder, willow, and cottonwood provide shade

34 Ecological Glacier Bay

35 4. 2 Energy Flow At the core of every organism s interaction with the environment is its need for energy to power life s processes

36 Producers Sunlight is the main energy source for life on Earth Less than 1 percent of all of the sun s energy reaches Earth Autotroph- capture energy from sunlight to produce food Plants, some algae, & certain bacteria Also called producers

37 Energy From the Sun Best known autotrophs are those that harness solar energy through photosynthesis Water + Carbon dioxide + sunlight Oxygen + Glucose Most life depends on photosynthetic organisms Rate at which organic material is produced by photosynthetic organisms in an ecosystem = primary productivity Determines the amount of energy available in an ecosystem On land, plants are main autotrophs In freshwater ecosystems, algae are primary producers Some wet ecosystems have cyanobacteria (photosynthetic bacteria)

38 Consumers Many organisms cannot harness energy directly from the physical environment Only way these organisms can acquire energy is from other organisms Heterotrophs: Organisms that rely on other organisms for their energy & food supply Also called consumers

39 Types of Consumers Herbivores: Eat only plants Carnivores: eat animals Omnivores: eat both plants & animals Decomposers: break down organic matter

40 Feeding Relationships Energy flows through an ecosystem in one direction from the sun or inorganic compounds to autotrophs (producers) and then to heterotrophs (consumers) The relationships between producers & consumers connect organisms into feeding networks based on who eats whom

41 Food Chains Food chains: a series of steps in which organisms transfer energy by eating and being eaten Always starts with a producer Arrows show the flow on energy; flows TO the organism that eats another organism

42 Food Webs Feeding relationships are more complex than can be shown in a single food chain Food web: links a group of interacting food chains

43 Tropic Levels Trophic level: A step in a food chain or food web shows how energy moves based on organism s source of energy

44 Trophic Levels 1st trophic level consists of producers 2 nd trophic level consists of herbivores 3 rd trophic level is usually omnivores; can be carnivores 4 th trophic level would be carnivores

45 Food Web

46 Food Web In most ecosystems, energy does not follow a simple path Animals feed at different trophic levels

47 Ecological Pyramids Ecological pyramids: a diagram that shows the relative amounts of energy or matter contained within each trophic level

48 Energy Pyramid Only 10% of the energy that is stored in one trophic level is passed on to the next level Rest of the energy is used by organisms for life processes such as respiration, movement, and reproduction, or loss as heat The more levels that exist between a producer and a top level consumer, the less energy that remains from the original amount

49 Trophic Levels LOSE 90% at each level

50 Energy Efficiency Adding a trophic level increases the energy demand of consumers by a factor of about 10

51 Limitations of Trophic Levels Usually only 3 trophic levels, too much energy lost at each level to allow for more levels Number of individuals may not be accurate indicator of amount of energy Some organisms are larger than others and use more energy Number of organisms often does not form a pyramid when looking

52 Biomass Pyramid Biomass: total amount of living tissue within a given trophic level Usually expressed in terms of grams of organic matter per unit area Biomass pyramids represent the amount of potential food available for each trophic level in an ecosystem

53 Limitations of Trophic Levels Most terrestrial ecosystems involve only three or, on rare instances, four trophic levels. Too much energy is lost at each level to allow more levels. The number of individuals in a trophic level may not be an accurate indicator of the amount of energy in that level. Some organisms are much bigger than others and therefore use more energy. Because of this, the number of organisms often does not form a pyramid when one compares different trophic levels.

54 Limitations of Trophic Levels To better determine the amount of energy present in trophic levels, ecologists measure biomass. Biomass is the dry weight of tissue and other organic matter found in a specific ecosystem. Each higher level on the pyramid contains only 10 percent of the biomass found in the trophic level below it.

55 4.3 Cycling The physical parts of the ecosystem are constantly cycling The paths of water, carbon, nitrogen, and phosphorus pass from the nonliving environment to living organisms, and then back to the nonliving environment. These paths form closed circles, or cycles, called biogeochemical cycles. In each biogeochemical cycle, a pathway forms when a substance enters living organisms such as trees from the atmosphere, water, or soil; stays for a time in the living organism; then returns to the nonliving environment.

56 The Water Cycle In the living portion of the water cycle, much water is taken up by the roots of plants. After passing through a plant, the water moves into the atmosphere by evaporating from the leaves, a process called transpiration. Transpiration is also a sun-driven process. The sun heats the Earth s atmosphere, creating wind currents that draw moisture from the tiny openings in the leaves of plants.

57 Steps of Water Cycle Water leaves plants through transpiration and enters atmosphere and becomes water vapor (in clouds) Water leaves clouds as precipitations Some precipitation can become runoff, meaning the water hits the ground and drains into a local lake, river, or ocean.

58 From the lake water can evaporate back into the atmosphere and become water vapor again Or it can seep into the soil from the lake through percolation and become groundwater. Ground water eventually rejoins a larger body of water from where it will evaporate again. The cycle continues on

59 The Water Cycle

60 Terms Precipitation: Any form of water, such as rain, snow, sleet, or hail, that falls to the earth's surface Transpiration: process of giving off water vapor, especially through openings on leaves Evaporation: change of a liquid into a vapor, takes place at the surface of a liquid Percolation: water passes through a porous substance, like soil and becomes groundwater

61 The Carbon Cycle In the carbon cycle, carbon atoms may return to the pool of carbon dioxide in the air and water in three ways: 1. Respiration Carbon dioxide is a byproduct of cellular respiration. 2. Combustion Carbon also returns to the atmosphere through combustion, or burning. 3. Erosion As the limestone becomes exposed and erodes, the carbon in it becomes available to other organisms.

62 Respiration Plants use CO2 during photosynthesis to make organic molecules (glucose) During this process they give off oxygen as a byproduct Then living organism use the oxygen to break down organic molecules to release energy. This process gives off CO2 back to the atmosphere.

63 The Carbon Cycle

64 The Phosphorus and Nitrogen Cycle Organisms need nitrogen and phosphorus to build proteins and nucleic acids. Phosphorus is an essential part of both ATP and DNA. Phosphorus is usually present in soil and rock as calcium phosphate, which dissolves in water to form phosphate ions phosphate ions.

65 Cont. The atmosphere is 79 percent nitrogen gas, N 2. The two nitrogen atoms in a molecule of nitrogen gas are connected by a strong triple covalent bond that is very difficult to break. However, a few bacteria have enzymes that can break it, and they bind nitrogen atoms to hydrogen to form ammonia. The process of combining nitrogen with hydrogen to form ammonia is called nitrogen fixation.

66 Nitrogen Cycle The nitrogen cycle is a complex process with four important stages: 1. Assimilation is the absorption and incorporation of nitrogen into plant and animal compounds. 2. Ammonification is the production of ammonia by bacteria during the decay of nitrogen-containing urea. 3. Nitrification is the production of nitrate from ammonia. 4. Denitrification is the conversion of nitrate to nitrogen gas.

67 Nitrogen Cycle