Sc chap 2

• Energy flow in an ecosystem

  The source of energy in all ecosystems originates from the Sun, where plants convert light energy into chemical energy through photosynthesis. This chemical energy is then transferred to primary consumers and then to secondary and tertiary consumers in the food chain and food web.
• Organisms in an ecosystem


  • Producers
  • Consumers
  • Decomposers
• Producer


  An organism that produces its own food through photosynthesis, most plants are producers
• Primary consumer


  A consumer that eats producers, herbivores and omnivores
• Secondary consumer


  A consumer that eats primary consumers, omnivores and carnivores
• Tertiary consumer


  A secondary carnivore that eats a secondary consumer, usually bigger than primary or secondary consumers
• Decomposer


  An organism that breaks down dead animals and plants into simpler materials or nutrients, known as saprophytism
• Decomposers


  • Mushrooms, mold, E. coli
• Food chain


  Shows the feeding relationships between organisms
• The interconnection of a few food chains is called a food web
• Energy is transferred from one organism to another in a food web, but some energy is lost as heat, undigested food, or faeces
• Nutrient cycle


  The continuous movement of nutrients from the environment, through living organisms, and back to the environment
• Water cycle


  The continuous movement of water from the Earth's surface to the atmosphere and back again
• Role of living things in the water cycle

  Plants absorb water through roots and release it into the atmosphere through transpiration, animals increase water content in the atmosphere through respiration, defecation and excretion, plant roots hold soil and reduce erosion, fallen leaves reduce evaporation
• Carbon cycle and oxygen cycle

  Plants and animals carry out respiration which uses oxygen and releases carbon dioxide, decomposition releases carbon dioxide, plants maintain the balance of carbon dioxide and oxygen through photosynthesis
• Human activities like logging, burning fossil fuels, and overconsumption of water negatively affect the nutrient cycle
• Steps to solve interference to the nutrient cycle

  • Create planned agricultural systems
  • Replant trees
  • Use public transport
  • Store rainwater for daily use
  • Tighten laws
• A species is a group of organisms that have similar characteristics and can reproduce to produce offspring
• Population


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


  A group of different populations of organisms that live together in the same habitat and have mutual interactions
• Ecosystem


  A community of living organisms and their physical environment interacting as a system
• A balanced ecosystem is in a state of harmony without any external interference, man-made ecosystems like aquariums may not be balanced
• Woodlice are more likely to gather in a damp place
• Variables


  • Constant variables: The number of woodlice, room temperature and light
  • Manipulated variable: Humidity
  • Responding variable: Distribution of woodlice
• The effect of humidity on the distribution of woodlice
• Problem statement: What is the effect of humidity on the distribution of woodlice?
• Hypothesis: Woodlice are more likely to gather in a damp place
• Material: Woodlice
• Apparatus: Petri dish with partition, wire gauze mould, Petri dish lid, anhydrous calcium chloride and stopwatch
• Tropical areas receive high distribution of rainfall and sunlight throughout the year
• Desert areas experience extreme hot and dry weather
• Tundra areas experience long winters and short summers
• Adaptation of Living Things to the Environment

  • How does wildlife adapt to the climate of their habitat in tropical, desert and tundra areas?
• Types of interaction between organisms

  • Symbiosis
  • Prey-predator
  • Competition
• Symbiosis


  When two or more organisms of different species live closely together and interact with one another
• Commensalism


  The interaction between two organisms which only benefits one organism without harming the other
• Commensalism


  • Remora fish and shark
• Prey-predator


  Involves one organism that eats another organism
• Prey-predator


  • Shark and fish
• Competition


  Organisms in one habitat compete for limited supply of basic needs such as light, space, water, food and mates