Biological Sciences: Ecosystems, Structures, and Inheritance
What to know
Living things interact with each other and with their environment. In an ecosystem, producers (plants, algae) capture sunlight and make their own food through photosynthesis; consumers eat other organisms; decomposers break down dead material and return nutrients to the soil. Food chains and food webs show energy flow, and the arrows always point from the organism being eaten to the one that eats it.
Organisms have structures that perform functions - a bird's hollow bones support flight, a cactus's thick stem stores water. Adaptations are inherited features that help survival in a particular habitat. Inherited traits come from parents (eye color, flower color); learned behaviors come from experience (a dog sitting on command, a bear learning where to fish).
Life cycles (seed → seedling → adult plant → flower → seed) show how organisms grow and reproduce. Classification groups organisms by shared characteristics. Populations are limited by food, water, shelter, space, predators, and disease.
Traps
- Reversing food-chain arrows - they show energy moving to the eater.
- Saying plants "eat" soil; they make sugar using sunlight, water, and carbon dioxide.
- Calling a learned behavior inherited (a trained trick is learned; fur color is inherited).
- Forgetting decomposers, which recycle nutrients instead of "eating" in the predator sense.
- Assuming removing one organism affects only one other; webs are interconnected.
Worked example
Food chain: grass → rabbit → hawk. If rabbits disappear, grass may grow more plentiful and hawks must find another food source or their population drops.
Rule of thumb
For any structure question, answer with the pattern structure → function → survival advantage.