Parent Primer: Life Science




It seems like life science should be simple, given that you live in the world and know the difference between an animal, vegetable, or mineral. But around 4th grade, when your child starts asking you what phylum a dolphin is in, you may find yourself floundering for the answer. Use this primer to refresh your memory on plant parts, ecosystem essentials, and all the other wonders of life so you can help your child's love of science flourish. To go even further with your science study, check out Everything You Need to Know About Science Homework, a great reference designed just for parents of budding scientists.

Defining Life:

One of the first science questions your child will learn to answer is, "Is it alive?" Some answers are easy: cats and dogs are alive, rocks and plastic bags are not. But what about a sponge or a virus? Your daughter can discover if something is a living thing — an organism — by seeing if it does the following six things:

  1. It takes in energy and gives off waste.
  2. It grows and develops.
  3. It can adjust to its environment.
  4. It can respond to its surroundings.
  5. It can reproduce.
  6. It is made up of cells.

All organisms can do these six things.

Classifying Life:

If something is living, it is also part of one of five groups, or kingdoms:

  • Animalia (Animals): Many-celled creatures that cannot make their own food, but instead must consume other animals and plants for energy. Their cells do not have rigid walls. Within the animal kingdom are mammals, birds, fish, amphibians, reptiles, mollusks, sponges, worms, insects, and spiders.
  • Plantae (Plants): Many-celled organisms that make their own food through photosynthesis. Their cells have rigid walls with cellulose in them. Included in the plant kingdoma are flowers, trees, moss, grass, and ferns.
  • Fungi (Fungus): Organisms that do not have chlorophyll, but instead dissolve their food and then absorb it. Their cell walls contain chitin. Includes mushrooms, molds, rusts, and yeasts.
  • Protista (Protists): Micro-organisms (mostly one-celled) that have cells with a nucleus. This kingdom includes algae, amoebas, paramecia, diatoms, and euglenas.
  • Monera (Monerans): One-celled micro-organisms that do no have a nucleus. Most absorb their food. Bacteria and thousands of other kinds of micro-organisms are part of the monera kingdom.

Once an organism's kingdom has been determined, scientists continue to separate out living things into smaller and smaller groups. This method of classifying helps people see what one animal might have in common with another. For instance, a dog and a cat both belong to the class of mammals, but they diverge at the genus level: cats are felines while dogs are canines.


Ecology is the study of the relationships between life and its environment. An ecosystem is any place where plants and animals live together and rely on each other in their natural surroundings or habitat. The largest ecosystem is the whole planet Earth, and it is called the biosphere. Most ecosystems that scientists (and your young scientist) study are much smaller, such as ponds, coral reefs, mountaintops, or fields. Sometimes scientists look at regions that share the same basic temperature and rainfall, like deserts, rain forests, and tundra. Each of these areas is called a biome. For more on the characteristics on the different climates, see the Geography Primer.

Any group of animals, plants, or other type of life that are the same species in the same area is called a population. All of the populations that live together in an ecosystem make up its community. When your child looks at an ecosystem, he might be asked how removing a population, such as frogs, would affect the community of a swamp. He will also study food chainsand natural cycles within ecosystems.

There are three natural cycles your student will become familiar with:

  • Water cycle: The sun drives the water cycle by heating water in lakes, rivers, oceans, and the soil, making it evaporate and turn into a gas. This water vapor rises into the atmosphere until gravity drags it down to earth again in the form of rain, snow, and dew. Most of the falling water returns right back to the ocean, but animals lap some up and some is absorbed by the soil where plants can drink it. The plants sweat out the water through transpiration, animals let out some water as waste, and when animals and plants decompose, their bodies release the water that makes up most of their mass.
  • Nitrogen cycle: Nitrogen is a crucial component for any form of life on Earth. The nitrogen cycle is the process of nitrogen being converted between its various forms, through such processes as fixation, mineralization, nitrification, and denitrification. Ecologists pay close attention to the nitrogen cycle because the ecosystem depends on nitrogen availability for important processes such as decomposition.
  • Oxygen and carbon cycle: Take two atoms of oxygen and one of carbon and you've got carbon dioxide (CO2), which is essential for photosynthesis. During this process, plants use the carbon to make food and new plant cells. Meanwhile, they release the oxygen that all animals breathe and plants use for respiration. The animals and plants then exhale CO2, and they also produce the essential gas during decomposition. Carbon also goes into long-term storage in the form of fossil fuels, such as coal and oil.
Sorting and Classifying
Subject Refreshers
Scientific Method
Memory and Memorization
Age 10
Age 9
Age 8
Plants and Flowers
Life Cycles
Water Cycle
Habitats and Ecosystems
Elementary School