Grade 6 Science: Organisms and Environments

Step 1: The living parts are biotic factors: the fish, the frogs, the cattails, and the insects the frogs eat.

Step 2: The nonliving parts are abiotic factors: sunlight, water, the range of temperatures, and the soil and rocks.

Step 3: Each organism depends on both: the cattails need sunlight and soil, the frogs need insects to eat, and the fish need water that stays cool enough.

Step 4: In a dry summer the pond shrinks. Now the frogs and fish compete for less water and less food, and some populations shrink.

Step 1: The owl hunts and eats the mouse. That is predation: the owl is the predator and the mouse is the prey.

Step 2: The two seedlings both need the same sunlight, water and soil, and there is not enough for both to grow big. That is competition.

Step 3: Competition can also be between different species: lions and hyenas compete for the same zebras.

Step 1: The bee gets nectar to eat, and the flower gets its pollen carried to another flower. Both are helped: mutualism.

Step 2: The tick feeds on the dog’s blood, and the dog is harmed. One is helped and one is harmed: parasitism.

Step 3: The bird gets a safe home, and the tree is not helped or harmed. One is helped and the other is not affected: commensalism.

Step 1: Organism: one white-tailed deer.

Step 2: Population: all the white-tailed deer living in that forest.

Step 3: Community: all the populations living there together: the deer, the wolves, the oak trees, the mushrooms and the birds.

Step 4: Ecosystem: the whole community plus the nonliving parts, like the sunlight, the stream, the soil and the weather.

Step 1: In 1665, Robert Hooke looked at thin slices of cork under a microscope and saw tiny boxes. He called them cells.

Step 2: In the 1670s, Antonie van Leeuwenhoek used his own powerful lenses to see living, moving microbes in pond water.

Step 3: In 1838 and 1839, Matthias Schleiden showed that plants are made of cells, and Theodor Schwann showed that animals are too.

Step 4: In 1855, Rudolf Virchow argued that every cell comes from a cell that already existed.

Step 1: Nucleus? A bacterium has none, so it is prokaryotic. An oak’s cells each have a nucleus, so it is eukaryotic.

Step 2: One cell or many? A bacterium is a single cell: unicellular. An oak has trillions of cells: multicellular.

Step 3: Makes its own food? The oak uses sunlight to make sugar, so it is an autotroph. Many bacteria take in food from around them, so they are heterotrophs.

Step 1: Peppered moths come in two variations: light and dark. Birds eat the moths they can see.

Step 2: On pale tree bark, the light moths blend in and the dark ones stand out, so more light moths survive and have young.

Step 3: Factory soot darkened the trees. Now the dark moths were hidden and the light ones stood out, so the dark moths survived better and became common.

Step 4: After cleaner-air laws, the bark lightened again, and the light moths became common again.