UNIT 2: ECOSYSTEM

• Green plants convert light energy from the Sun into chemical energy through the process of photosynthesis. The chemical energy is transferred to primary consumers and then to secondary and tertiary consumers in the food chain and food web
• Producers

  • A producer is an organism that produces its own food through photosynthesis. Most plants are producers
• Primary consumers

  • A consumer is an organism that eats another organism. Primary consumbers are herbivores and omnivores that eat producers. For example, caterpillars
• Secondary consumer

  • A secondary consumer is an omnivore and carnivore that eats the primary consumer. For example, the himalayan bluetail, Tarsiger rufilatus, is an omnivore because it eats caterpillars and fruits. However, the kingfisher, Alcedo atthis, is a primary carnivore because it eats primary consumers such as snails, fish tadpoles and shrimps
• Tertiary consumers

  • A tertiary consumer is a secondary carnivore that eats a secondary consumer. The size of a tertiary consumer is ususlly bigger than a primary or secondary consumer
• A food chain can be used to show the feeding relationship between organisms
• The interconnection of a few food chains is called a food web
• Energy is transferred from one organism to another organism in the food web. Some energy is lost because it is used by the organism to move and carry out the life process of respiration. Energy is also lost in the form of heat energy, chemical energy through undigested food or faeces.
• Role of living things in the water cycle

  • Water is absorbed by roots of plants in the ground and released into the atmosphere through transpiration. Animals carry out respiration, defecation and excretion (sweating and urination). All of these increase the water content in the atmosphere
  • Roots of plants hold the soil tightly and make the structure of the soil more compact. This slows down the flow of water underground and prevents soil erosion.
  • Leaves that fall from trees and cover the surface of the earth will reduce the rate of evaporation and prevent the soil from becoming dry
• The role of living things in the carbon and oxygen cycle

  • Plants and animals carry out respiration which uses oxygen and releases carbon dioxide.
  • The decay of dead plants and animals by bacteria and fungi in the soil uses oxygen and releases carbon dioxide.
  • Green plants maintain the content of carbon dioxide and oxygen in the air through photosynthesis which absorbs carbon dioxide and releases oxygen
• Human activities that disrupt the nutrient cycle

  • Unrestricted logging
  • Burning of fossil fuels
  • Overconsumption of water resources
• Steps to solve interference the nutrient cycle

  • Create planned agricultural systems
  • Use public transport
  • Store rain water for daily use
  • Replant trees
  • Tighten laws
• Habitat

  • A habitat is the natural surroundings or home of an organism
• Species

  • A species is a group of organisms that have common characteristics and can reproduce to breed offsprings
• Population

  • A population is a group of organisms of the same species that live in the same habitat
• Community

  • A community is a few populations of different organisms that live together in one habitat and have mutual interaction with one another.
• Ecosystem

  • An ecosystem is a few communities that live together in one habitat and have mutual interaction with one another including all the non-living components such as water, air and soil
• Symbiosis happens when two or more organisms of different species live closely together and interact with one another.
• Mutualism is an interaction that benefits both organisms.

  EXAMPLES

  1. The sea anemone protects the clown fish from predators and supplies food to it. The clown fish cleans the sea anemone and provides nutrients to the sea anemone in the form of waste.
  2. Lichens are algae and fungi that live together. The fungi supply water and minerals to the algae. The algae carry out photosynthesis and supply food to the fungi.
  3. The mynah gets food from the buffalo by eating the lice that stick to the body of the buffalo. The body of the buffalo is free of lice.
• Commensalism is the interaction between two organisms which only benefits one organism without harming or benefitting the other. Commensal is the organism that benefits.

  1. The remora fish (commensal) latches on the shark (host) and gets its food from scraps scattered by its host.
  2. The bird's nest fern (commensal) grow in between the branches of trees (host) to get sunlight.
• Parasitism is an interaction that benefits one organism only and harms the other. Parasite is the organism that benefits. Host is the organism that is harmed.

  1. The tapeworm (parasite) that lives in the human intestine (host) absorbs nutrients.
  2. Lice (parasite) suck the blood of humans and animals (host)
• Prey predator

  • involves one organism that eats another organism
  • Prey is the organism that is eaten by the predator.
  • Predator is the organism that hunts another organism for food
• Competition

  • Competition happens when organisms in one habitat compete for limited supply of basic needs such as light, space, water, food and mates
• Biological control is a method that uses organisms that are natural predators, parasites or pathogens to reduce the number of pests in an area
• Owls are kept in palm oil plantations to control the population of rats
• Bacillus thuringiensis is used to control pests, namely the rhinoceros beetle in palm oil plantations
• The guppy is a predator to mosquito larvae in a pond
• The ladybird beetle eats aphids, a crop pest
• Ducks are reared in paddy fields to eat pests such as snails and insects
• Biological control is more environmental friendly because it does not use pesticides or chemicals. This method is usually cheaper and does not affect humans' health. This method has a few weaknesses such as

  • it takes a long time before any effect is seen
  • the balance of the ecosystem might be disrupted because a new species is introduced in the ecosystem
• Factors that Influence Population Size in an Ecosystem

  • disease
  • presence of predators
  • source of food
  • change of weather
• Disease

  • The population of animals and plants decreases when a disease strikes. For example, avian flu in poultry-rearing areas and tobacco mosaic virus in tobacco crops
• Presence of predators

  • The population size of a living organism is influenced by the population size of its predator. For example, the size of the zebra population in the savanna ecosystem decreases with the presence of its predators such as the lion
• Source of food

  • If a food source decreases, animals can be threatened by extinction. For example, panda depends on bamboo as its primary food source. Clearing of forests has caused the destruction of its food source and habitat. In Malaysia, the crow population has increased due to the abundance of food scraps
• Change of weather

  • Droughts cause soil to become dry and infertile and increase the risk of forest fires. As a result, the population of plants and animals decreases.
• Limited Water Supply

  • Paddy is a plant that requires a lot of water
  • If there is a long drought season, this change in the ecosystem will upset the balance between population in the paddy field.
  • The food web will be affected because the population of the producer which is paddy, decreases
• Migration

  • The ecosystem can also change because of animal migration, moving from one place to another due to a change of season
  • For example, the cattle egret (Bubulcus ibis) migrates to Kuala Gula, Perak from September to April every year. As a result, the number of insects such as grasshoppers, crickets, spiders, flies and worms decreases as they are eaten by the egrets.