ENVIRONMENTAL BIOLOGY. Part 4

Transcription

1 ENVIRONMENTAL BIOLOGY Part 4

2 Overview: A) THE BIOSPHERE B) POPULATION ECOLOGY C) COMMUNITY ECOLOGY D) ECOSYSTEM ECOLOGY E) THE CARBON & NITROGEN CYCLES F) ECOLOGICAL TECHNIQUES G) SIMPSON S RECIPROCAL INDEX H) LOCAL ECOLOGY I) BIOLOGICAL DIVERSITY

3 Two processes proceed concurrently in ecosystems: ENERGY FLOW SUN Light energy Biotic component Heat energy The movement of: 1. ENERGY linear renewed all the time nutrients Abiotic component 2. NUTRIENT ELEMENTS cyclic originates from the abiotic component

4 The SUN is considered the ultimate source of energy as it: provides energy to almost all organisms. Plants get energy directly from the sun. These organisms get energy indirectly from the sun.

5 Bacteria are the base of the food chain at hydrothermal vents. These bacteria use sulfur compounds, particularly hydrogen sulfide, a chemical highly toxic to most known organisms, to produce organic material through the process of chemosynthesis.

6 Producers: harness energy from the sun e.g. plants, algae Consumers: organisms that eat something else e.g. animals Ulva lactuca Decomposers: return energy to the environment e.g. fungus, bacteria

7 The terms detritivore and decomposer are often used interchangeably Detritivores - small animals like earthworms, crabs that feed on detritus springtail Detritus: fragments of decaying material

8 What do decomposers and detritivores have in common? BOTH receive energy from decayed matter Fungus: DECOMPOSER Spider crab: DETRITIVORE

9 How do they differ? Detritivores: eat the organic matter Decomposers: 1. secrete enzymes to digest organic matter 2. then absorb the ensuing molecules

10 The decomposers are a special subset of detritivores that: break the organic compounds in inorganic form and then

11 The decomposers are a special subset of detritivores that: break the organic compounds in inorganic form and then absorb whatever they need for nutrition

12 Consumers Vultures Four types Herbivore: eats only plants E.g. Cows, horses Carnivore: eats only meat E.g. Polar bear Omnivore: eats plants and animals E.g. Humans, bears Scavenger: carnivore that feeds on bodies of dead organisms e.g. Vultures

13 Food Chains & Food Webs

14 A Food Chain is the: energy flow from one trophic level to the other One organism at each trophic level.

15 What does an arrow show? The direction of the energy transfer, NOT what ate what Rose Aphid Ladybug

16 A Trophic Level describes the position of the organism in relation to how it gets nutrients & energy The main trophic levels are: Primary producers Consumers Decomposers

17 Primary producers: Photosynthesisers: - are autotrophs: get their energy directly from sunlight Consumers & Decomposers are: Heterotrophs: consume, directly or indirectly, the energyrich molecules made by the primary producers

18 Trophic Levels [Feeding Levels] heterotrophs autotrophs

19 Organisms in one trophic level feed in the same way 4 th Trophic Level 3 rd Trophic Level 2 nd Trophic Level 1 st Trophic Level Terrestrial food chain Aquatic food chain

20 Two Types of Food Chain: Detritus food chains Grazing food chains Leaf litter

21 Two Types of Food Chain: 1. grazing food chains grass rabbit fox eagle 2. detritus food chains leaf litter earthworm blackbird dead animal blowfly maggots frog (detritus detritivore carnivore) blowfly maggot

22 What is a Food Web? When more than one organism is present at each trophic level

23 When compared to food chains, Food Webs are: Reticulate (resembles a network) more stable more resistant to disruption If all deer die, do bears starve to death? NO!!

24 Note how: energy flows in ONE direction BUT ALL the matter ends up in the detritivores & decomposers

25 Energy Losses in Ecosystem

26 How much of the solar energy falling on a leaf is used for photosynthesis? only about 1% What happens to the rest of the solar energy falling on a green leaf?

27 The light energy which is not absorbed by a leaf is: Sunlight 100% Reflected 15% Evaporation 75% Transmitted 5% Can a plant absorb ALL wavelengths of light?

28 White Light NO. Certain wavelengths of light cannot be absorbed (e.g. green) Leaf Pigments Absorb Most Colors

29 Why do leaves look green? Green wavelength is reflected

30 Question: Give FOUR reasons why not all the light energy reaching a plant can be used for photosynthesis. 1) Light is reflected away by the cuticle; 2) Light may not be of the correct wavelength such as the green wavelength; 3) Light is not trapped by chloroplasts but passes right through the leaf - transmitted; 4) Light heats up water inside the leaf and makes it evaporate.

31 What is the photosynthetic efficiency? Sunlight 1880 x 10 6 kj m -2 yr -1 Reflected Evaporation Photosynthesis 24 x 10 6 kj m -2 yr -1 Transmitted 1880 x % 24 x 10 6? 24 x x 10 6 x 100 = 1.3%

32 Why does a food chain rarely have more than 7 trophic levels? Substantial losses in energy at every trophic level

33 Energy is lost at each trophic level. What could cause the energy to be lost? Heat Movement Waste e.g. feces, urine Respiration Uneaten parts e.g. bones, fur, shells, wood

34 Which portion will be available to the next trophic level?

35 Energy Losses in Ecosystem Only about 10% of energy passes through each step of a food chain 90% of energy is lost at each step

36 If the pea plant contains 100 units of energy, how much energy would be present in the hawk?

37 Why are energy losses greater in homeotherms (birds & mammals) than in poikilotherms (fish, reptiles)? -have to do something to maintain body temperature Homeotherms use a great proportion of food eaten to keep a constantly warm body temperature. Hea t Heat

38 Question: This cow has eaten 100 kj of stored energy in the form of grass, and lost 63 kj in the form of faeces, urine and gas. The energy stored in its body tissues is 4 kj. So how much has been used up in respiration? The energy released by respiration: Eaten: 100 Lost: 63 Kept: (63 + 4) = 33 kj

39 Question: Only 4 kj of the original energy available to the cow is available to the next stage, which might be humans. What is the efficiency of this energy transfer? Efficiency = = 4%

40 Explain the following observation: Average efficiency of transfer from: plants to herbivores = 10% from animal to animal = 20% 10% 20% Herbivores are less efficient than carnivores as they eat grass having material which is not digestable (lignin & cellulose).

41 Question The diagram shows the transfer of energy through a cow. The figures are in kj 10 6 year 1. Key: A = energy absorbed from the gut C = energy consumed in food F = energy lost in faeces P = energy used in production of new tissue R = energy lost by respiration U = energy lost in urine

42 a) (i) Complete the following equation for the energy used in the production of new tissue. Use only the letters C, F, R and U. (1) P = C (U + F + R)

43 ii) Calculate the value of P. (2) P = C (U + F + R) = ( ) = = 3.74 kj x 10 6 year -1

44 Production Ecology

45 Productivity / Production refers to the rate of generation of biomass (the total mass of organisms in a given area or volume) in an ecosystem per unit area per unit time unit is: joules/m 2 /year (energy) or g/m 2 /year (dry organic matter)

46 Two types of Productivity: Primary: productivity of autotrophs (plants) Secondary: productivity of heterotrophs (animals) Glucose formed CO 2 Food eaten O 2 H 2 O

47 Primary Productivity is the rate at which energy is stored by primary producers in the form of organic substances which can be used as food materials

48 Gross Primary Production (GPP): GPP the rate at which plants store chemical energy and is entirely available for growth NPP NPP = GPP - R Net Primary Production (NPP): the energy potentially available to the next trophic level

49 NPP = GPP - R Glucose produced during photosynthesis (Gross Primary Production) Remaining glucose available to be laid down as new material - biomass (Net Primary Production) Some glucose is used to supply energy to drive cellular processes (Respiration)

50 Net Primary Productivity NPP = GPP - Respiration plant 50% of GPP is used for respiration

51 Biomass / Standing Crop the amount of dry organic matter per unit area present at a given time Unit of biomass: g/m 2 OR the amount of stored food energy per unit area present at a given time Unit of biomass: J/m 2

52 Productivity and Biomass DO NOT mean the same!! Productivity is the RATE at which organic matter forms. There is no element of time involved in the definition of biomass.

53 Productivity refers to the rate of generation of biomass in an ecosystem per unit area per unit time. Its unit is joules/m 2 /year. Biomass refers to the amount of dry organic matter per unit area present at a given time. Its unit is g/m 2. There is no element of time involved in biomass.

54 Give a reason why an ecosystem can be highly productive but has a low biomass. It is rapidly grazed

55 It is rapidly grazed

56 Secondary Production: The conversion of assimilated energy into new tissue by animals Energy assimilated = Food eaten Faeces Total energy taken in (food eaten) Waste (faeces)

57 How much energy is available to the next trophic level?

58 REMEMBER: Respiration, maintenance Gross primary production (GPP) Net primary production (NPP)

59 Components of energy transfer between trophic levels Energy from lower trophic level Energy not used Egested energy Urinary waste Gross energy intake Digested energy Assimilated energy Resting energy Activity Growth Reproduction Maintenance or respiration Production

60 Comparisons of Community Production Community Climate Kcal/m 2 /yr Desert Arid 400 Lake Temperate 2,400 Deciduous Temperate 4,800 Forest Tropical Tropical 20,000 Rainforest Cropland Temperate 8,800 Salt marsh Temperate 12,000 Freshwater marsh Temperate 17,000

61 What is the correlation in each case? Positive correlation

62 Coral Reef: High productivity

63 Factors that influence Primary Productivity include: Temperature Intensity of sunlight (which varies seasonally)

64 Generalisations about Community Productivity The tropics have among the most productive systems, in part because incident solar radiation is greater toward the equator. The most productive temperate systems are marshes. Nutrients are continually brought in and wastes are flushed out as water moves through them. Deserts and oceans are among the least productive systems. Little water in deserts and few nutrients in open oceans are responsible. Thus, 80% of the Earth s surface is covered by the least productive systems.

65 Energy Flow Through A Grazing Food Chain

66 Energy Flow Through A Grazing Food Chain

67 WORKED OUT PROBLEM: FLOW OF ENERGY (kj/m 2 /yr) IN A GRASSLAND

68 1) Find the gross primary production of grasses and herbs. 36x x10 6 = 24x10 6 kj/m 2 /yr

69 2) Find the photosynthetic efficiency (i.e. efficiency of conversion of incident solar energy to gross primary production. 1880x % 24x10 6 x 100 = 1.3% 24x10 6? 1880x10 6

70 3) What is the net production of seed-eating birds, spiders and grasshoppers respectively? i) Birds: 60x x10 3 = 800 kj/m 2 /yr

71 3) What is the net production of seed-eating birds, spiders and grasshoppers respectively? ii) Spiders: = 200 kj/m 2 /yr

72 3) What is the net production of seed-eating birds, spiders and grasshoppers respectively? iii) Grasshoppers: 444x x10 3 = kj/m 2 /yr

73 Pyramids

74 What are Ecological Pyramids? diagrammatic representations of feeding relationships and energy transfer through the biotic component of ecosystems

75 Three types of Ecological Pyramids: 1. Numbers 2. Biomass 3. Energy Secondary consumers Primary consumers Producers

76 Pyramid of Numbers: Nos. at each trophic level Tertiary Consumer 1 eagle 4 th Trophic Level Secondary Consumer 8 frogs 3 rd Trophic Level Primary Consumer 29 grasshoppers 2 nd Trophic Level Producers 1500 blades of grass 1 st Trophic Level

77 What happens to the population size on moving up the pyramid? Decreases Tertiary Consumer 1 eagle 4 th Trophic Level Secondary Consumer 8 frogs Primary Consumer 29 grasshoppers 3 rd Trophic Level 2 nd Trophic Level Producers 1500 blades of grass 1 st Trophic Level

78 Pyramid of Numbers may be inverted: Typical pyramid with a carnivore Inverted pyramid with a LARGE producer Inverted pyramid with PARASITES

79 How would you collect data to draw a pyramid of fresh biomass for a field ecosystem? A quadrat is placed at random. All organisms enclosed are collected. Organisms are separated into various trophic levels: producers, herbivores & carnivores. Organisms at each trophic level are weighed. Biomass in g m -2 is calculated. Procedure is repeated to get an average. A pyramid is drawn to scale.

80 How would you know to which trophic level an organism belongs? 1. Observe an animal while it feeds. 2. Inspect mouthparts. 3. Dissect ONE animal and observe gut contents.

81 How is a pyramid drawn to scale? Organisms Fresh biomass / g Green plants 2250 Herbivores 240 Carnivores 38 Green plants: 2250/38 = 59 boxes Herbivores: 240/38 = 6 boxes Carnivores: 38/38 = 1 box Divide each number by the smallest value.

82 Pyramid of Biomass Why is the pyramid inverted in autumn? Low food production by producers & a lot of grazers

83 Draw a pyramid of numbers & of biomass for this food chain: Pyramid of Numbers Ladybird Aphid Rosebush Pyramid of Biomass Rosebush Aphid Ladybird

84 90% Loss in energy at EACH trophic level Pyramid of Energy kj/m 2 /day

85 Why does biomass decrease up a food chain? As energy is consumed by the organisms at each trophic level, less energy is available to organisms further along the food chain which thus supports a smaller biomass

86 Four reasons why the pyramid of energy: is the ideal way of representing relationships between individuals because:- 1. it takes into account the rate of production (flow of energy in a specific time) Energy Flow kj/m 2 /day Biomass grams/m 2 Forest

87 2. Comparison based on biomass may be misleading because weight for weight two species may not have the same energy content 3. inverted pyramids are not obtained

88 Pyramid of Energy: Different ecosystems can be compared and the relative importance of populations within one ecosystem can be compared For example, the great importance of soil bacteria in terms of energy flow is not obvious from their small biomass Soil bacteria Marine snails Density Biomass Energy flow (No./m 2 ) (g/m 2 ) (kj/m 2 /day)

89 Pyramid of Energy: 4. input of solar energy can be added as an extra rectangle at the base of the pyramid

90 Criticisms of ecological pyramids 1. It is difficult to allocate a trophic level to many carnivores and omnivores which eat a varied diet. 2. Another major problem is where to place dead and waste material. Way to show decaying material in a pyramid of biomass or energy.

91 Overview: A) THE BIOSPHERE B) POPULATION ECOLOGY C) COMMUNITY ECOLOGY D) ECOSYSTEM ECOLOGY E) THE CARBON & NITROGEN CYCLES F) ECOLOGICAL TECHNIQUES G) SIMPSON S INDEX H) LOCAL ECOLOGY I) BIOLOGICAL DIVERSITY

92 A simple definition of biodiversity: is the number and types of organisms in an environment Three levels of diversity:

93 Biological Diversity: refers to the diversity of life in all its forms, levels and combinations it must be expressed at three levels: 1) Ecosystem diversity 2) Species diversity 3) Genetic diversity

94 END OF SECTION