Chapter 7.4 Nutrient Cycles

1. Chapter 7.4Nutrient Cycles

2. Learning Objectives • By the end of the lesson, you should be able to: • show an understanding of the new concept of recycling of nutrients trapped in living organisms and explain the role of decomposers in these processes • describe briefly the carbon cycle • discuss the role of the carbon cycle in helping to maintain a balance in the ecosystem

3. Importance of Nutrient Cycles • Living things on earth are primarily made up of the following elements: • Carbon • Hydrogen • Oxygen • Nitrogen • Phosphorus • Sulfur • They also require the following compound as the main solvent/medium in which biochemical processes take place within: • Water

4. Importance of Nutrient Cycles • While the Earth receives a continuous input of solar energy from the Sun, the total amount of each of the elements on Earth remains relatively constant since the formative stages of our planet. • i.e. The Earth does not receive additional amount of carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur after it is formed. • Hence, as plants and animals grow and die, they cycle these elements between the environment and their bodies through various: • biological processes such as photosynthesis, cellular respiration and decomposition. • And geological processes such as sedimentation. • And processes arising from the action of human beings such as deforestation and burning of fossil fuel.

5. The Carbon Cycle Burning of fossil fuel Deforestation Respiration Photosynthesis Stored in plant tissues Respiration Decomposition Stored as fossil fuel

6. Chapter 7.6Conservation

7. Learning Objectives By the end of the lesson, you should be able to: explain the importance of conserving the physical environment predict the consequences of selective addition or removal of an organism from an environment

8. Stability in an Ecosystem • Dynamic flow of energy • Cycling of nutrients • Intricate interactions between organisms Stability & Self-sustainability in the Ecosystem • If ecosystem is stable and self-sustainable  balanced • This balance requires: • A constant input of energy. • Presence of producers which are able to harness this source of energy, converting it into chemical energy required to power the rest of the food chain. • A continuous circulation of matter between the biotic and abiotic components of an ecosystem. • Hence, an ecosystem can be destabilized if any of the above three criteria are not met. This leads to its collapse.

9. Ecosystem Stability & Biodiversity • Every component (biotic or abiotic) of the ecosystem plays a role in maintaining the ecosystem’s stability. • Reason: • Energy passages through them • matter is cycled through them • they play various roles as producers, consumers and decomposers. • Since every organism plays very specific yet important roles in an ecosystem, the entire set of organism (i.e. the variety of organisms) found in the ecosystem is required to maintain its balance. • Analogy: A machine needs all its components to work. Gears, levers, fan belt, bolts and nuts etc. One goes missing and the machine will fail.

10. Why Conserve Biodiversity? • prevent extinction • maintain stability in the ecosystem • maintain large gene pool thus preserving useful genes • Sources of raw materials  economic, medical and industrial • scientific value – study of evolution • recreational purposes such as hiking, fishing, skiing

11. What is Biodiversity? • Biodiversity is the variety of living organisms (i.e. distinct biological species) and their range of behavioral, ecological, physiological and other adaptations in an area such as an ecosystem. • Consists of three levels: • Genetic diversity • Species diversity • Ecosystem diversity

12. Genetic Diversity • The variety of genes in a population of organisms. • Genes are pieces of hereditary information found in structures known as chromosomes • These structures are in turn found in the nucleus of dividing cells.. • Genes determine character traits such as green eyes, brown eyes, ability to roll tongue etc. • Thus together, the many individuals of a species contribute to the genetic diversity of that species.

13. Species Diversity • Total variety of biological species in a given place. • Two organisms are considered as members of two different species if they are unable to produce a viable offspring that is itself capable of reproduction. • E.g. chimpanzees, gorillas, humans, tigers, elm trees, orchid plants, bracket fungi, Pseudomonas bacteria, Amoeba

14. Ecosystem Diversity The variety of ecosystems found in the biosphere. The destruction of one ecosystem, will destroy many of the organisms that live within it, decreasing both species and genetic diversity.

15. Removing Species from an Ecosystem • Extinction due to: • Introduction of natural predator • Introduction of competitor • Depletion of food and water resources • Sterility • Low birth rates • Environmental stressors • Loss of habitat • Poaching for food or pet trade

16. Addition of New Species • Addition of new species may also destabilize an ecosystem • Example: Biological Pest Control • A method of pest control involving the release of the natural predator of the pest. These predators prey on the pest (by predation, herbivory or parasitism) and decimate the pest population. • Disadvantage • Predator may also prey on local endemic species • Pest population may not be controlled • Pose as competition to other species Invasive species – The Cane Toad