2. Man’s place in nature Classification of man Animal: cannot make own food but must obtain food from plants or other animals Vertebrate: with backbone Mammal (same group as cat, cow, horse & dolphin) Primate (same group as monkey, tarsier & chimpanzee)

3. 1) hair present 2) no eggs laid but young born alive after a period of development inside the mother’s body 3) Young fed on milk produced by the mother’s mammary glands after birth 4) Parental care well developed (young dependent on and protected by the parents for a period of time) 5) Homoiotherm - can maintain constant and relatively high body temperature to be active even at low environmental temperature Characteristics of Mammals

4. Characteristics of Primates 1) Brains relatively larger than those of other mammals so that they have great learning power and a high intelligence. 2) Both eyes face forward instead of being situated at the sides of the head. Hence, good judgment of distance. 3) Have a flat face and a short snout 4) Have opposable thumb - thumb touching fingers of the same hand to grasp objects with hands (e.g. man holding tools and monkey holding tree branches). It is also separated from other fingers, all of which end at a nail.

5. Unique biological features of man 1) Upright posture, with head held vertically on the vertebral column, to free the hands from walking 2) Body weight supported on 2 legs during walking or standing due to broad and strong pelvic girdle, longer and stronger hindlimb (or foot bones) than forelimb 3) Better developed opposable thumb to grip objects more strongly and to manipulate objects and tools precisely and skilfully, aided by the eyes at the front of the head 4) Large cerebrum, resulting in development of complex tools, languages, culture & man’s dominance

6. Ecology: The study of the interaction between organisms and their physical environment, and with other organisms. Habitats: They are defined regions in the natural world. Each habitat has a particular set of physical conditions in which an organism lives Physical conditions include temperature, humidity and soil type

7. Mangrove Forest Freshwater stream Grassland Various habitats on Earth:

8. Each habitat is occupied by a characteristic community of organisms, which is made up of different populations

9.  Habitat: the place where an organism occurs  Population: a group of organisms of the same species in an area  Community: populations of all the different organisms in the same area

10. Ecosystem: A dynamic and self-supporting system where organisms interact with each other and with their environment The components of an ecosystem

11. What does the environment refer to? The environment of an organism made up of: –an abiotic part (physical environment) –a biotic part (other organisms in the surroundings) These affect the number, distribution, behaviour and types of organisms in a habitat

12. What are abiotic factors? The abiotic factors arise from the non-living components in the environment. They differ between habitats The major abiotic factors are: –Temperature –Light –Rainfall and humidity –Wind –Soil

13. What are biotic factors? Arise from other organisms in the environment Organisms interact with each other in various ways, and these may be beneficial or harmful to each other The major interactions are -Predation -Competition -Commensalism -Mutualism -Parasitism

14. Energy flow in an Ecosystem Sunlight The ultimate source of energy Plants and algae Chemical energy in organic molecules Eaten by Animals Absorbed by Converted to Energy is transferred in the form of organic materials within an ecosystem

15. Feeding relationships like this are usually expressed in a food chain or a food web

16. A particular feeding relationship and sequence of energy flow between organisms in a habitat can be shown as a food chain Examples: –In a grassland Grass Rabbit Snake Hawk –In a freshwater pond Algae Water flea Shrimp Fish What are food chains and food webs?

17. Food chain: over-simplifies the natural situation. Food web: a more accurate representation of the energy relationship, which shows all the possible feeding relationships between organisms in a habitat Example: In a grassland:

18. What are the roles of organisms in an ecosystem? The three main roles of organisms in an ecosystem: Producer, consumer and decomposer Decomposers are not shown in food chains Producers All food chains starts with producers. Include all autotrophic organisms such as plants and algae. Provide energy for the organisms in the ecosystem

19. Consumers Consumers are organisms that feed on other organisms Primary consumers: Animals that feed on plants (Herbivores) Secondary consumers: Animals that feed on primary consumers (Carnivores) Tertiary consumers: Animals that feed on secondary consumers (Carnivores) Primary consumer Secondary consumer Tertiary consumer

20. Humans play various roles in food chains. We can be primary, secondary or tertiary consumers With reference to your daily diet, try to work out your position as a consumer in the various food chain.

21. Organisms that break down organic materials (e.g. dead bodies and waste products) into simple, inorganic substances, which can be used by the plants again. Important in recycling materials in the ecosystem Mainly bacteria and fungiDecomposers

22. Secondary consumer Tertiary consumer What are trophic levels? Each level of organisms in a food chain is called a trophic level Example: GrassProducerFirst Rabbit Primary consumer Second SnakeThird HawkFourth Example of organism in a food chain Types of organism Trophic level

23. How energy is transferred between trophic levels? Producers convert light energy into chemical energy which is stored in organic molecules. When the producers are eaten, this chemical energy is transferred to the next trophic level. Thus, energy is transferred along the food chain

24. How energy is transferred between trophic levels? However, a small proportion of energy can be transferred to the next trophic level due to energy loss at each level: 1.Consumed during respiration. The energy released is given off as heat or used to support body activities 2.Lost in the form of wastes and excretory substances 3.Lost when the organisms die without being consumed

25. Energy loss means that some energy cannot be transferred to the next trophic level The wastes and dead bodies are broken down by decomposers, and the chemical energy stored is used by them

26. Some energy trapped by producers is also released to the environment as heat. Hence, a continuous supply of light energy is essential for the growth and activities of organisms in the ecosystem

27. Investigation of a Balanced Aquarium

28. Why is it necessary to use tap water which has been standing for a few day ? Ans: Because fresh tap water contains chlorine which is harmful to organisms in the aquarium. lid water water snail freshwater plant

29. Why is it unsuitable to introduce large carnivores into the glass jar ? Ans: Because they require more food to survive and they will eat up all the organisms in the aquarium. lid water water snail freshwater plant

30. Describe the appearance of the water snails and the freshwater plants after a few days if the aquarium is balanced ? Ans: The water snails and the aquatic plants will remain healthy even after a few weeks. lid water water snail freshwater plant

31. What will happen to the aquarium if it is placed in darkness all the time ? Why ? Ans: Both the water snails and the freshwater plants will gradually die since there is no light for the aquatic plants to carry out photosynthesis to make food … lid water water snail freshwater plant

32. What will happen to the aquarium if it is placed in darkness all the time ? Why ? Ans: The plants cannot survive without food supply. As all aquatic plants died, the water snails also die due to starvation. lid water water snail freshwater plant

33. What is the relationship between trophic levels? The total amount of energy available to each trophic level become progressively less along a food chain This relationship can be expressed by using: -The pyramid of numbers -The pyramid of biomass

34. Pyramid of numbers The number of organisms in a higher trophic level is usually smaller because: -The amount of energy available decreases along a food chain -A predator is usually larger than its prey In a pyramid of numbers, the width of each bar represents the number of organisms at a trophic level Why does a large body size leads to a small number of organisms in a trophic level?

35. Drawbacks of the pyramid of number: It only considers the numbers of organisms, but not the amount of energy stored in their bodies An inverted pyramid of numbers can result from organisms with a very large size Can you give another example of a food chain showing an inverted pyramid of numbers?

36. Biomass: the total dry mass of organisms at a certain trophic level. The pyramid of biomass is a more accurate representation of the energy transfer because: -The amount of energy stored in an organism is usually proportional to the amount of living materials in its body Pyramid of biomass

37. There is a limit to the length of food chain (< 5 links) because: -Energy is continuously lost along the food chain, the energy available to organisms at higher trophic levels becomes progressively less. The pyramid of biomass shows that the lower trophic levels contain more energy  we can obtain more food from a piece of land if we use it for growing crops rather than rearing cattle To know more about the energy flow in an ecosystem, visit: http://web.ukonline.co.uk/webwise/spinneret/ eco/ecosys.htmhttp://web.ukonline.co.uk/webwise/spinneret/ eco/ecosys.htm

38. How are toxic substances accumulated along a food chain? Pests are organisms that can damage our crops Pesticides are poisonous chemicals used to kill pests Some pesticides are very stable compounds. They can stay inside organisms for long periods without being broken down by metabolism or excreted. These will accumulate along food chains and may reach an amount high enough to kill organisms at higher trophic levels

39. Example: the pesticide called DDT (a pesticide) - Widely used in the past - It is a large molecule that cannot be excreted or broken down by metabolic processes

40. Accumulation effect of DDT: Consumers feed on a relatively large quantity of organisms in their lower trophic level  A higher concentration of DDT accumulated in their body  DDT became more and more concentrated along the food chain  Reach a toxic level in the bodies of the fish and birds Thus, the use of DDT has been banned in many countries What is the effect of DDT on humans?

41. Introduction Producers Inorganic substances Complex organic substances Other organisms Synthesize By feeding Respiration Faeces, excretory products and dead bodies Decomposers Decompose by CYCLING OF MATERIALS

42. How does the cycling of carbon occur in the ecosystem? Carbon is an important component of carbohydrates, fats, proteins, nucleic acids and other substances essential to the life of organisms The continuous movement of carbon between organisms and the physical environment is the carbon cycle

43. The carbon cycle 44

44. Carbon Cycle Carbon dioxide in air organic substances in plants organic substances in animals assimilation & photosynthesis respiration fossil fuel feeding respiration burning incomplete decomposition

45. Removal of carbon dioxide from the atmosphere and water In atmosphere: Carbon is present as carbon dioxide in the atmosphere In water bodies: Carbon is present as dissolved carbon dioxide, carbonates and hydrogencarbonates Ways of removal of carbon in nature: 1.Producers take up carbon by photosynthesis to produce organic substances. 2.Through feeding, the organic molecules are transferred to the bodies of different consumers along the food chain

46. Return of carbon dioxide to the atmosphere and water 1.Respiration carried out by all organisms breaks down organic compounds, and releases carbon in the form of carbon dioxide back to the environment 2.Decomposition of the dead bodies and organic wastes by decomposers released carbon back to the environment Ways of return of carbon:

47. Large number of organisms are buried due to movement of the Earth’s crust. They are turned into fossil fuels such as coal and oil (petroleum) Through burning, the carbon present in fossil fuels and wood are returned to the atmosphere as carbon dioxide To know more about the carbon cycle, visit: http://www.smy.fi/koulut/carbon/

48. How does the cycling of nitrogen occur in the ecosystem? Nitrogen is an essential component of proteins, nucleic acids and other nitrogen- containing compounds The nitrogen cycle describes the cycling of nitrogen in ecosystems The nitrogen cycle 45

50. Though 78% of air is nitrogen, they cannot be used directly by most organisms. They are made available by the activity of nitrogen fixing bacteria living freely in the soil or in the root nodules of leguminous plants such as peas and beans which convert atmospheric nitrogen into nitrates. This process is called nitrogen fixation. 1.Atmospheric nitrogen may also react with oxygen to form nitrogen oxides by electrical discharges during lightning. These oxides are dissolved in rain water and carried to the soil to form nitrite and nitrate.

51. Cycling of nitrates among organisms Plants obtain nitrogen mainly in the form of nitrates in the soil water, which they then assimilate into proteins. Animals obtain nitrogen compounds through feeding along food chains, so that plant proteins are assimilated into animal proteins. Nitrate can be recycled due to breakdown of dead organic matter: Dead organic matter Ammonia or ammonium compound Nitrites Decomposed by putrefying bacteria and fungi Oxidized by nitrifying bacteria by a process called nitrification Nitrates

52. Though nitrates can be absorbed by the plants from the soil water, some may be: -Lost from the soil by leaching in rain water -Changed to atmospheric nitrogen by the action of denitrifying bacteria, which are active when the soil is poorly aerated. The process is called denitrification. To know more about the nitrogen cycle, visit: http://web.ukonline.co.uk/webwise/spinneret/ eco/cycles.htmhttp://web.ukonline.co.uk/webwise/spinneret/ eco/cycles.htm

53. In natural habitats: The processes which remove and replace nitrates in the soil are in balance. In agricultural lands: A large amount of nitrogen in the organic matter is removed by harvesting. Fertilizers must be added to the soil to maintain crop yield. Actually, fertilizers are made by some industrial process involving nitrogen reacting with hydrogen using catalyst. To know more about the ecosystem, visit: http://resources.ed.gov.hk/biology/english/ind ex.htmlhttp://resources.ed.gov.hk/biology/english/ind ex.html

54. Nitrogen cycle

55. The oxygen cycle Atmospheric oxygen is used up in respiration and combustion to form carbon dioxide and water. Oxygen is produced in photosynthesis

56. The water cycle

57. Water evaporates from surface of water bodies such as oceans, lakes and soil. The water vapour in clouds condenses in the atmosphere and is returned to the earth as rain or snow. Water is lost by evaporation through the general body surface and respiratory surface. Plants absorb water through their roots and land animals obtain water mainly from food to replace water lost.

58. Introduction Organisms living in a habitat interact with each other in various ways. These interactions directly or indirectly affect their distribution, abundance and behaviour These interactions include: –Predation –Competition –Symbiosis

59. What is predation? When one organism (predator) kills and feeds on another organism (prey), the relationship is known as predation In predation, the predators are benefited while the preys are harmed Consider a caterpillar and a bird. Which is the predator and which is the prey? How about the bird and the hawk?

60. Predation (Predator-prey relation) Time Number prey predator HareLynx The predator-prey relationship determines the relative abundance of the predators and the preys. The relationship also means that the distribution of predators and preys are closely related. For example, grasshoppers are only found where there is abundant grass.

61. When the number of preys increases, more food is available to the predators and so they also increase in number. Increased predation, however, leads to a decrease in the number of preys. This in turn causes a drop in the predator population. As the predators become less abundant, the number of preys rises again. This type of interaction therefore results in a periodic fluctuation in the number of predators and preys

62. What is competition? The relationship in which two organisms compete with each other for certain common needs Common needs: food, water, space, light, mate, etc. Two types of competition: 1.Intraspecific competition Competition between members of the same species. Example: Trees in a woodland compete for light and water

63. Interspecific competition Competition between different species. Example: Different types of fish compete for prey in the same habitat The more similar the needs, the greater is the competition Intraspecific competition is usually greater than interspecific competition All involved organisms are harmed In a grassland, lizards and toads compete for insects as their food. If the lizards are removed from the grassland, what will happen to the number of toads? Why?

64. Time Number Competition (competitors) the winner the loser Cuckoo displacing the host ’ s egg In the food web of the grassland, both lizards and toads compete for the same food, the grasshoppers. If the lizards are removed from the habitat, the number of toads will increase due to less competition for food.

65. What is symbiosis? The relationship in which two species are so closely associated with each other that they actually live together 3 types of symbiotic relationships: –Commensalism –Mutualism –Parasitism

66. Considering the barnacles and the crabs. Which are commensals and which are hosts? One species (the commensal) benefits, the other (the host) is unaffected The attachment of barnacles on a crab: - The crab provides transport and a surface for attachment to the barnaclesCommensalism The crab does not gain or lose anything from the association

67. Both species gain benefits by living together The attachment of sea anemone on the shell dwelled by a hermit crab: - The sea anemone obtains scraps of food from the hermit crab and gains mobilityMutualism - The hermit crab gains camouflage and gains protection from the sea anemone which possesses sting cells

68. Nitrogen-fixing bacteria living in the root nodules of leguminous plants: - The bacteria obtain carbohydrates from the host for energy supply -The bacteria supply nitrogenous compounds to the plant to synthesise protein In some cases, the organisms are so dependent on each other that they cannot live independently

69. Fungus and alga in lichens: - Lichens are made up of these two organisms - The fungus depends on the alga for the supply of carbohydrates - The alga depends on the fungus for inorganic nutrients, moisture and protection etc

70. One species (the parasite) lives inside or on the body surface of another species (the host) The parasite gains advantages while the host suffers from this associationParasitism The tapeworm: - A parasite living in the small intestine of humans - Absorbs digested food through its body surface - The host may suffer from malnutrition