GRADE 12 IEB LIFE SCIENCES/BIOLOGY NOTES HUMAN POPULATION DYNAMICS:food chain and food web

1. Food chain: Draw a food chain and indentify the producers, primary, secondary and tertiary consumers. Identify the herbivore, omnivores and carnivores. Dandelion plant Aphid Ladybug Robin Producers: dandelion plant Primary consumer: Aphid Secondary consumer: Ladybug Tertiary consumer: Robin Herbivore: Aphid Omnivore: Ladybug Carnivore: Robin 2. Discuss how the food chain can be affected and the implications for the ecosystem. • If an organism is removed from the food chain due to a certain cause, it disrupts the entire food chain • For example: if the dandelion plant goes extinct, the aphid population would decrease due to not having the nutrients from the plant anymore. The other organisms would also be affected. 3. What percentage of the energy is passed on from one organism to another? Explain. • The percentage of energy passed on from one organism to another is 10% • The energy that is not transferred to the other organism is usually used by the organism passing the energy. They use the energy for body function, which is released as heat or the energy passes out as waste by the organism. 4. What is population density? How it is measured? What is the difference between dependent and independent factors that can affect a population? Give examples. • Population density: the number of individuals of the same species that occur per unit area or volume D= N S D: Population density N: total amount of individuals of the same species S: The area or space occupied by the population 5. Explain the symbiotic relationships between organisms. Define predation, competition, mutualism, commensalism, and parasitism. Give examples. • Symbiotic relationship between organisms: Symbiosis, meaning "living together" refers to a relationship in which individuals of two difference species live in close, usually physical contact • Predation: an ecological interaction in which a predator catches, kills, and consumes prey