CHAPTER 4: CHARACTERISTICS IN ECOSYSTEMS

Transcription

1 1 CHAPTER 4: CHARACTERISTICS IN ECOSYSTEMS 4.3. FACTORS AFFECTING ECOSYSTEMS Pages Nelson

2 1. ABIOTIC FACTORS IN TERRESTRIAL ECOSYSTEMS 2 abiotic factors are the non-living components of an ecosystem affect the type and number of organisms that can live there Describe abiotic components that cause the two terrestrial ecosystems below?

3 3 I. Physiographic Factors physical features of a geographical area a) Latitude - higher latitudes: less solar energy input, varied day lengths with seasons b) Altitude - higher altitudes: cooler temps, more wind, poorer soil c) Topography - physical features of land (ex: mountains, river valleys). May affect precipitation.

4 4 II. Climatic Factors a) Light - amount affects the rate of photosynthesis and therefore food chains b) Temperature - limits the type of organisms that can survive c) Moisture - certain plants and animals are adapted to dry environments d) Wind- affects soil; increases heat and water loss by organisms e) Fire - periodic burning is necessary in some ecosystems ---> unlocks nutrients stored in biomass of trees; increases sunlight to forest floor

5 III. Edaphic Factors 5 factors related to soil soil contains both organic and inorganic matter site of decomposition of dead organic matter; matter returns to producers vegetation slows soil erosion and prevents water runoff Abiotic factors are called limiting factors because they restrict or limit the number and types of organisms able to survive in a particular environment. belts of climate determine result in distinct vegetation patterns the vegetation of a region determines which consumers can and will continue to exist there these zones are called biomes

6 2. Abiotic Factors in Fresh Aquatic Ecosystems (p104) 6 1. Oxygen lakes and ponds get some O 2 from atmosphere, but most from photosynthetic plants fast flowing rivers get major source of O 2 from aeration lowest acceptable limit is 5 ppm (5 parts of O 2 per million parts water) conc. of O 2 in the water decreases as the temperature increases

7 7 2. Carbon Dioxide respiration by living organisms is the major source the surface contains very little but the bottom has higher levels due to respiration by decomposers; mostly bacteria 3. ph healthy range is usually between 6.7 to 8.6 acid rain can cause ph levels to drop, making aquatic enviro. unable to support life 4.Temperature each species has a preferred temp. with most species, an increase by 5C is harmful as the water temp goes up, the ability to hold O 2 goes down, yet the animal needs more O > or dies 5. Light increased light means increased P/S and higher plant productivity

8 3. Structure of Lakes and Ponds Read pages and make notes on Seasonal Variations in Canadian Lakes: define epilimnion, hypolimnion, thermocline. (plants have roots) (light) (too dark for photosynthesis) 8 Benthic zone

9 4. Wetlands 9 Bogs are usually located in regions where temperatures are cool for much of the year Marshes and swamps are usually located near coastal areas in warmer climates Swamps and marshes differ in the size of plant life they will support Marshes have small plants such as reeds, cattails, and grasses Swamps contain such larger plants as cypress trees and Spanish moss A variety of waterfowl and shorebirds live in swamps and marshes These wetlands also provide shelter to animals such as muskrats, frogs, turtles, snakes, alligators, fish, and raccoons

10 Large numbers of insects, such as beetles, dragonflies, and mosquitoes, are common in bogs Bogs also have a variety of plants that grow well in the organically rich, partially decayed plant material called peat Peat forms much of the bog soil One of the most unusual bog plants is the pitcher plant 10

11 Section 4.3 Tasks 11 Read Pages in your textbook Complete Section 4.3 Questions Page # s 1-4, 7 Make some notes on Seasonal Variations in Canadian Lakes Nelson page

12 Section 4.3 Questions (Page 107) The amount of organic matter in an ecosystem can increase through runoff from soil, surface waters, fertilizer use, release of sewage emissions, litter from plant material, animal wastes, and die-offs of plants and/or animals, etc. 2. It is possible to have two ecosystems with identical rainfall and temperature support different plants. For example, Europe and North America both have deciduous forest ecosystems with similar temperatures and rainfall. Both have tall trees, shrubs, ferns etc., but since they are in different geographic locations, the species of each plant type might be different. 3. The oxygen concentration in the hypolimnion is high initially due to spring turnover. The oxygen concentration gradually falls as the oxygen is consumed by bacteria that decompose dead plant and animal materials. In extreme situations, oxygen may be completely consumed.

13 P107 Continued The lower, cooler layers of water have no source of oxygen input, so it is gradually consumed. The surface layers receive more oxygen when wind and waves disturb the surface, allowing oxygen to dissolve. 7. Trout can exist only in cooler, oxygen-rich waters. They survive below the thermocline in lakes that stratify and remain high in oxygen, not in shallower, warmer waters. Catfish are always found close to the bottom since they are bottom feeders. They can live in shallow, warm waters and can also tolerate low oxygen levels. Neither of these situations can support trout.

14 4.4 LIMITS ON POPULATIONS AND COMMUNITIES IN ECOSYSTEMS 14 Pages

15 Biotic Potential (p108) 15 Field mice can reproduce every 6 weeks and can have litters of 6 or more. A population of 20 mice could become 5120 mice in six months! What factors prevent a population explosion of mice? Biotic potential is the maximum number of offspring that a species could produce if resources are unlimited Regulated by four factors: birth potential (max #/birth), capacity for survival (# reach reproductive age), breeding frequency, and length of reproductive life (age of sexual maturity and # of fertile years)

16 Limiting Factors and Carrying capacity 16 Recall that limiting factors are factors that restrict or limit the number and types of organisms able to survive in a particular environment Limiting factors prevent populations from obtaining their biotic potential The carrying capacity is the maximum number of individuals that can be supported by an ecosystem At what level do the deer reach their CARRYING CAPACITY?

17 Density-Independent and Density Dependent Factors 17 Density-Independent factors affect a population regardless of population density Density-Dependent Factors affect the size of a population as a result of population density What are examples for each type of limiting factor? Unsure, go to page 111, and copy table 2 into your notes!

18 Tasks to be completed: 18 Read Section 4.4 in your Text Pages Complete the Section 4.4 Questions Pages , 5

19 4.5 CHANGES IN ECOSYSTEMS 19 Pages Nelson

20 Changes in Terrestrial Ecosystems 20 Read Pages of your textbook Write down the main ideas on forestry practices including clear-cutting, slash-and-burn, and prescribed burns. Be prepared to discuss the pros and cons for each technique!

21 Ecological Succession The Process of Succession Describe the community in the picture on the right. Ecological succession is a community change in which new populations of organisms gradually replace existing ones Succession occurs from natural causes (competition, fire, earthquakes, etc) or due to man (logging, mining, farming etc) 21

22 Primary Succession Succession that begins in an area where there is no existing community Causes of prim Succession: volcanic eruption, glacier retreat The first group of organisms to occupy an area undergoing primary succession is called a pioneer community Pioneer organisms must be hardy and able to live on minimal resources Lichens are pioneer organisms Primary Succession Animation 22

23 Steps in Primary Succession: 23 Glacier Retreats exposing Parent rock Pioneer community (lichens, mosses) Soil formation (lichens die/ break up rock) Increased soil = shallow rooted trees (pine) Grasses die = more soil = shrubs and weeds take over Enough soil = grasses out compete lichens Increased pine = more shade = favorable for deeply rooted plant (maple/ birch) Climax Community

24 Primary Succession: Primary Succession Animation 24

25 Secondary Succession Secondary succession: occurs in an area where an existing community has been partially destroyed Examples: Fires, logging, farming Occurs more rapidly then primary succession A community that achieves relative stability is called a climax community Climax communities tend to have greater species diversity than the communities that precede them 25

26 26 Changes in Aquatic Ecosystems 1. Index Species when water becomes polluted, there tends to be a shift from MANY species of moderate population density to a FEW species of high population density > index species this decrease in the diversity of species present is the best indicator of pollution 2. Eutrophication definition: the natural process of SLOWLY aging or increasing productivity of a body of water

27 pollution increases the natural eutrophication process of water. Why? Unnatural Eutrophication: a process in which nutrient runoff from agricultural lands or livestock operations causes photosynthetic organisms in ponds and lakes to multiply rapidly Human-caused eutrophication wiped out fisheries in Lake Erie in the 1950s and 1960s 27

28 LAKE EUTROPHICATION High levels of P and N containing compounds (fertilizers/ detergents) Algal Bloom Algae die = food for decomposers = population grows Low oxygen = other organisms die out Decomposers break down material and use up oxygen in lake Water in which oxygen becomes too low to support animal life is called eutrophic To protect Canadian lakes, ponds, and streams from becoming eutrophic, some states no longer allow the sale of detergents containing phosphorus compounds 28

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30 Dr. David Schindler is an ecologist who worked at the Experimental Lakes Project in northern Ontario He performed several classic experiments on eutrophication that led to the ban on phosphates in detergents 30

31 Classification of lakes by the nutrient input which also determines the primary producers. Oligotrophic lake: Nutrient-poor, photosynthesis-limited, clear water, O 2 rich. Eutrophic lake: Nutrient-rich, high photosynthesis, murky water, O 2 poor. 31

32 Tasks to be completed: 32 Read Chapter 4.5 in your textbook Pages Make your own notes on: Forestry Practices page The effects of fire page 115 Indicators of Water Quality Pages 117 Biological Oxygen Demand (BOD) Page 118 Complete Section 4.5 Questions Page 122 #5 Chapter 4 Review: P130 #1-8