Food web (1) 2

food web and food chain

1. University of the Punjab Lahore

2. Food Web

3. Community A group of organisms living in the same environment.

4. Living organisms (biotic factors) Producers Consumers Primary consumers Secondary consumers Tertiary consumers Quaternary consumers Decomposers

5. Producers: Plants are called producers because they are able to use light energy from the Sun to produce food (sugar) from carbon dioxide and water. The process by which plants make food is called photosynthesis.

6. Consumers: Animals cannot make their own food so they must eat plants and/or other animals. They are called consumers . There are mainly three groups of consumers but sometimes we also include quaternary consumers also.

7. Primary consumers : Animals that eat ONLY PLANTS are called herbivores and are also called primary consumers.

8. Secondary consumers: Animals that eat OTHER ANIMALS are called carnivores . Carnivores that eat herbivores are called secondary consumers.

9. Tertiary consumers Carnivores that eat other carnivores are called tertiary consumers.

10. Quaternary consumers organisms that eat tertiary consumers.

11. Decomposers: A final link in the food chain are decomposers which break down the organic matter of the tertiary consumers (or whichever consumer is at the top of the chain) and release nutrients into the soil.

12. Abiotic components

13. Food Chain History : Food chains were first introduced by the African-Arab scientist and philosopher Al-Jahiz in the 9th century and later popularized in a book published in 1927 by Charles Elton, which also introduced the food web concept.

14. What is food chain? A food chain represents the series of transfer of energy in different levels of community. Example: Grass Grasshopper Snake Hawk Fungi

15. Trophic levels The  trophic level  of an organism is the position it occupies in a food chain.

16. Food Web

17. What is food web? Food web can be defined as, "a network of food chains which are interconnected at various tropic levels, so as to form a number of feeding connections amongst different organisms of a biotic community". It is also known as consumer-resource system. It is a graphical description of feeding relationships among species in an ecological community. It is also a mean of showing how energy and materials (e.g., carbon) flow through a community of species as a result of these feeding relationships.

18. Food web basics: A node is one of the words/pictures that the arrows go toward or away from. A node may represent an individual species, or a group of related species or different stages of a single species (such as one node for adult frogs and a second for juvenile tadpoles). A link connects two nodes. Arrows represent links, and always go from prey to predator (as in food chain). The lowest trophic level are called basal species The highest trophic level are called top predators. Movement of nutrients is cyclic but of energy is unidirectional and non-cyclic.

19. Types of food web representation: Topological webs Flow webs Interaction webs

20. Topological webs Early food webs were topological. They simply indicate a feeding relationship. One problem… Suppose individuals of species X eat 10,000 individuals of species Y, and one X is seen eating one individual of species Q. A topological web then shows an arrow from Y to X, and an arrow from Q to X. This makes it look as though both prey are equally important to X. But they’re not!

21. Flow webs Bioenergetic webs, or flow webs, include information on the strength of the feeding interaction. This can be done in one of two ways: Vary the size of the arrow. Thicker arrows represent a larger percentage of the diet. (interactions where more prey are eaten or where more energy flows upward). The amount of energy moving between nodes next to the arrow.

22. Interaction web An interaction web is similar to a topological web, but instead of showing the movement of energy or materials, the arrows show how one group influences another. In interaction food web models, every link has two direct effects. One of the resource on the consumer and one of the consumer on the resource.  The effect of the resource on the consumer is positive, (the consumer gets to eat) and the effect on the resource by the consumer is negative (it is eaten). 

23. Different food webs Soil food web Aquatic food web Food web in forest Food web of grassland Food web in terrestrial and aquatic ecosystem

24. The soil food web The  soil food web  is the community of organisms living all or part of their lives in the soil. It describes a complex living system in the soil and how it interacts with the environment, plants, and animals.

25. The soil food web The soil food web is similar to the food chain, except that the typical food chain is linear, while the soil food web shows everything that can eat or be eaten in a cyclical relationship.  Soil is composed of two parts: Minerals, which make up the nonliving portion of the soil. Minute creatures, also called soil biota, which bring the soil to life. Soil biota come in many forms. Some help to build healthy soil and support healthy plants, and these are considered beneficial. Others can cause many problems and are considered pathogens.

26. Critters of soil food web: BACTERIA: Our native soils are full of bacteria, both beneficial and pathogenic. In general, they help water move through the soil more easily, they recycle organic matter, and they help ward off soil diseases. There are many types of bacteria, but one of the most important groups is the nitrogen-fixing bacteria. They create a waste product called bacteria manure that adds new forms of organic content to soil. Many plants absorb nutrients most efficiently through this bacterial waste product, so the more nitrogen-fixing bacteria in the soil, the better it is. Bacteria and bacteria’s waste products are also eaten by fellow soil dwellers of many kinds, so they feed other organisms in the soil in addition to feeding plants.

27. EARTHWORMS: Worms are among the most beneficial of soil dwellers. Sadly, they are easily harmed or killed by exposure to many common pesticides and herbicides. Actually they are the soil builders. They do the mixing of soil. They tunnel through heavy soil to let air get down to plant roots.

28. The aquatic food web food chain which occurs in aquatic water is called aquatic food chain. e.g.    Algae  →   Protozoa   →   Small Insects   →    Large aquatic Insects   →    Small fish  →   Large fish

29. The aquatic food web A balanced food web is essential to any marine or fresh water system, and can be an indicator of habitat quality. Planktonic algae are the foundation of aquatic food webs. . The size and diversity of the planktonic algae community determines the diversity of the zooplankton community that can be supported as well as the small fish community.

30. The aquatic food web

31. Functions of Aquatic food web The main function of Aquatic food chain is that: It depicts the structure of the living components of hydrosphere. It transfers energy and materials.

32. Food web in forest

33. Food web of grassland

34. Food web in terrestrial and aquatic ecosystem

35. Why energy is transferred? Ecosystem maintain themselves by cycling energy and nutrients obtained from external sources.

36. Energy Flow In ecology,  energy flow , also called the  calorific flow , refers to the flow of energy through a food chain. .

37. Gross primary production Gross primary production consists of the amount of light energy that is converted to chemical energy by photosynthesis per unit of time. This chemical energy is going to two places-- respiration and growth of new biomass.

38. Net primary production Some fraction of this fixed energy is used by primary producers for cellular respiration and maintenance of existing tissues. The remaining fixed energy is referred to as net primary production  .

39. History : H. T. Odum analyzed the flow of energy through a river ecosystem in Silver Springs, Florida. His findings are shown here. The figures are given in kilocalories per square meter per year ( kcal/m 2 /yr ).

40. Findings: At each trophic level, Net production is only a fraction of gross production because the organisms must expend energy to stay alive. Much of the energy stored in net production was lost to the system by decay being carried downstream Conversions efficiencies are always much less than 100%.

41. How many levels can ecosystem support? Terrestrial not more than 5. Marine not more than 7.

42. A general energy flow scenario follows: Solar energy is fixed by the photoautotrophs, called primary producers, like green plants. Primary consumers absorb most of the stored energy in the plant through digestion, and transform it into the form of energy they need, such as adenosine triphosphate (ATP), through respiration.

43. A general energy flow scenario follows: Secondary consumers, carnivores, then consume the primary consumers, although omnivores also consume primary producers. Tertiary consumers, which may or may not be apex predators, then consume the secondary consumers, with some energy passed on and some lost, as with the lower levels of the food chain.

44. A general energy flow scenario follows: A final link in the food chain are decomposers which break down the organic matter of the tertiary consumers (or whichever consumer is at the top of the chain) and release nutrients into the soil. The energy is passed on from trophic level to trophic level and each time about 90% of the energy is lost

45. A general energy flow scenario follows: Therefore, primary consumers get about 10% of the energy produced by autotrophs, while secondary consumers get 1% and tertiary consumers get 0.1%.

46. Energy pyramid An ecological pyramid (or tropic pyramid) is a graphical representation designed to show the biomass or biomass productivity at each tropic level.

47. overall energy flow in ecosystem

48. significances of food web Food webs distinguish levels of producers and consumers by identifying and defining the importance of animal relationships and food sources, beginning with primary producers such as plants, insects and herbivores. Food webs are important tools in understanding that plants are the foundation of all ecosystems and food chains, sustaining life by providing nourishment and oxygen needed for survival and reproduction. In short the food web provide stability to the ecosystem.

49. Effects on food web man is disturbing the food chain and making it short. The shortening of food chain due to man’s activities leads to imbalance in the functioning of an ecosystem and ultimately the biosphere.