11.2 Life Science: Organisms, Habitats, Traits & Ecosystems

Life Science: Organisms, Habitats, Traits & Ecosystems

Quick Answer: Living things are made of cells, grow, reproduce, respond to stimuli, and use energy. Organisms pass through predictable life cycle stages, depend on habitats, and interact through food chains and webs. Inherited traits are passed through genes; learned behaviors develop through experience. The cell is the basic unit of life.

What Makes Something Alive?

Living things share key characteristics:

• Made of cells (the basic unit of life)
• Grow and develop
• Reproduce
• Respond to stimuli (plants turning toward light, earthworms pulling away from touch)
• Use energy (from food or sunlight)
• Produce wastes

A classic comparison: an earthworm is made of cells, grows, reproduces, and responds to touch — it is alive. A burning candle uses energy (oxygen) and produces wastes (smoke), but it is not made of cells, does not grow on its own, and does not reproduce, so it is not alive.

Basic Needs of Living Things

All organisms need:

• Air (oxygen for most animals; carbon dioxide for plants)
• Water (for body processes and photosynthesis)
• Food or energy (food for animals; sunlight for plants)
• Shelter (protection from weather and predators)
• Space (room to grow and reproduce)

Life Cycles

Organisms pass through stages from birth to reproduction to death. Comparing life cycles helps students see patterns and differences.

Both butterflies and chickens hatch from fertilized eggs. Frogs undergo metamorphosis — a dramatic change in body form from an aquatic tadpole to a land-dwelling adult. Flowering plants produce seeds that germinate when conditions (water, warmth, air) are right.

Habitats and Adaptations

A habitat is the place where an organism lives and finds what it needs: a pond for a frog, a forest for a deer, a garden for a butterfly. Within any habitat, organisms compete for food, water, shelter, and space. When a habitat changes — from a drought, wildfire, or human activity such as building a road — the organisms that live there must adapt, move, or perish.

An adaptation is a trait that helps an organism survive in its habitat. Adaptations can be structural (thick fur in cold climates, cactus spines that reduce water loss, webbed feet for swimming, camouflage that hides prey from predators), behavioral (birds migrating south in winter, wolves hunting in packs), or functional (a chameleon changing color, a person sweating to cool down). Georgia's own coastal salt marsh gives students a local example: cordgrass has aerenchyma tissue that lets its roots survive in salty, waterlogged soil.

When a habitat changes faster than organisms can adapt, populations shrink. Protecting habitats through parks, refuges, and responsible land use helps maintain biodiversity.

Food Chains and Food Webs

Energy flows from the Sun through producers to consumers to decomposers.

A food chain shows one path of energy: grass → rabbit → hawk. A food web links many chains together in an ecosystem — a community of living and nonliving things interacting. Predator and prey describe one organism eating another. A biome is a large region with a similar climate and organisms, such as a desert, rainforest, tundra, or Georgia's own coastal salt marsh.

Inherited Traits vs. Learned Behaviors

• Inherited traits are passed from parents through genes: eye color, leaf shape, number of legs. Instincts are inherited automatic behaviors — a spider spinning a web, a bird building a nest.
• Learned behaviors develop through experience and practice:
  • Imprinting — learning a parent figure shortly after birth (ducklings following their mother)
  • Conditioning — learning by repeated association (Pavlov's dogs salivating at a bell)
  • Trial-and-error learning — a child learning to ride a bike

A dog's fur color is inherited; a dog sitting on command is learned.

Survival Factors and Conservation

Survival depends on habitat, food, water, predators, disease, and climate. When these factors fail, populations decline. Endangered species are at risk of extinction — Georgia's right whale and the loggerhead sea turtle are examples. Conservation protects organisms and habitats by recycling, reducing pollution, preserving wetlands, planting trees, and protecting nesting sites.

Cells and Classification

The cell is the basic unit of life. Organisms are classified into major groups:

• Plants — make food by photosynthesis, have cell walls
• Animals — consume food, can move
• Fungi — decomposers that absorb nutrients (mushrooms, mold)
• Protists — mostly single-celled organisms (amoeba, paramecium)
• Bacteria — single-celled organisms without a nucleus

Understanding classification helps students see the diversity of life and how organisms relate through shared characteristics.