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84 lessons · 3rd Grade
Pollination happens when pollen moves from one flower to another, often carried by bees, butterflies, or wind. This process allows plants to produce seeds and fruit.
All living things share basic characteristics: they grow, reproduce, respond to their environment, and need energy to survive. Plants make their own food through photosynthesis, while animals must eat other organisms.
Habitats provide everything an organism needs to survive: food, water, shelter, and space. Different habitats like forests, deserts, and oceans support different types of life.
Food webs show the complex feeding relationships in an ecosystem. Unlike a simple food chain, a food web shows that most organisms eat more than one type of food.
Animals have different adaptations that help them survive. Camouflage helps animals blend in, sharp claws help predators catch prey, and thick fur keeps animals warm.
A food chain shows how energy passes from one organism to another. Producers like plants capture energy from the sun, herbivores eat the plants, and carnivores eat the herbivores.
Decomposers like fungi and bacteria break down dead organisms and return nutrients to the soil. Without decomposers, dead material would pile up and nutrients would be locked away.
During metamorphosis, an organism changes its body form completely. A butterfly begins as an egg, becomes a caterpillar, forms a chrysalis, and finally emerges with wings.
Plants reproduce through seeds or spores. Flowering plants produce seeds inside fruits, while conifers produce seeds in cones. Ferns and mosses reproduce using tiny spores.
Many animals migrate to find food, warmer weather, or safe places to have their young. Birds, whales, and monarch butterflies are famous for their long migration journeys.
Hibernation is a deep sleep that helps animals survive winter when food is scarce. During hibernation, an animal's heart rate and breathing slow down to save energy.
Predator-prey relationships help keep ecosystems balanced. When prey populations increase, predator populations grow too. When predators reduce prey numbers, predator populations then decline.
Ecosystems include all the living and nonliving things in an area that interact with each other. A pond ecosystem includes fish, frogs, algae, water, rocks, and sunlight.
Living things are organized into levels: cells form tissues, tissues form organs, organs form organ systems, and organ systems make up a complete organism.
Vertebrates have backbones and include fish, amphibians, reptiles, birds, and mammals. Invertebrates lack backbones and include insects, spiders, worms, and jellyfish.
Plants have specialized structures: roots anchor the plant and absorb water, stems transport materials, leaves capture sunlight, and flowers produce seeds for reproduction.
Symbiosis is a close relationship between two different species. In mutualism, both benefit; in parasitism, one benefits while the other is harmed; in commensalism, one benefits and the other is unaffected.
Organisms in an ecosystem depend on each other. Producers make food, consumers eat other organisms, and decomposers break down dead material to recycle nutrients.
The life cycle of a frog includes egg, tadpole, tadpole with legs, froglet, and adult frog. This process of metamorphosis takes several weeks to months depending on the species.
Biomes are large regions with similar climate, plants, and animals. Major biomes include tropical rainforest, desert, grassland, tundra, and temperate forest.
Animal behaviors can be innate (born with) or learned. A spider spinning a web is innate behavior, while a dog learning to sit on command is learned behavior.
Photosynthesis converts light energy into chemical energy stored in glucose. Plants use carbon dioxide from the air and water from the soil, releasing oxygen as a byproduct.
Coral reefs are underwater ecosystems built by tiny coral animals. They support an incredible diversity of marine life including fish, sea turtles, and invertebrates.
Plants need sunlight, water, carbon dioxide, and nutrients from soil to grow. Their roots absorb water and minerals while their leaves capture sunlight for photosynthesis.
Endangered species are at risk of extinction due to habitat loss, pollution, hunting, or climate change. Conservation efforts work to protect these species and their habitats.
Seeds contain a tiny plant embryo and a food supply. When conditions are right—enough water, warmth, and oxygen—the seed germinates and a new plant begins to grow.
Animals can be classified as herbivores (plant eaters), carnivores (meat eaters), or omnivores (eating both plants and animals). Their teeth and digestive systems are adapted to their diet.
Succession is the gradual change of an ecosystem over time. Primary succession begins on bare rock, while secondary succession occurs after a disturbance like a fire.
Animals communicate using sounds, body language, colors, and chemical signals called pheromones. Communication helps them find mates, warn of danger, and mark territory.
Wetlands like marshes and swamps filter water, prevent flooding, and provide habitat for many species. They are among the most productive ecosystems on Earth.
