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Biology (ATC)

A community-written study guide covering every topic on this event's official test plan. Sign in to contribute to a section.

1Describe the study of life and levels of organization

10% of exam

Biology is the study of living things and their organization.

  • Life is organized from atoms → molecules → cells → organisms → ecosystems.
  • All living things share traits: growth, reproduction, metabolism, and response.
  • The cell is the basic unit of life.
  • The scientific method guides biological inquiry.

2Describe the structures and functions of plant and animal cells

20% of exam

Cells have specialized parts called organelles.

  • The nucleus holds DNA; mitochondria make energy (ATP).
  • Ribosomes build proteins; the ER and Golgi process and ship them.
  • Plant cells add a cell wall, chloroplasts, and a large vacuole.
  • The cell membrane controls what enters and leaves.

3Describe the mechanisms of genetics and heredity

20% of exam

Genetics explains how traits pass from parents to offspring.

  • Genes on chromosomes carry hereditary information.
  • Mendel's laws describe dominant/recessive inheritance.
  • Punnett squares predict offspring ratios.
  • Alleles, genotype, and phenotype describe genetic makeup and traits.

4Apply the principles of evolution

10% of exam

Evolution explains how species change over time.

  • Natural selection favors traits that aid survival and reproduction.
  • Darwin proposed descent with modification.
  • Evidence includes fossils, anatomy, and DNA.
  • Adaptation and variation drive evolutionary change.

5Describe evolution and biodiversity

10% of exam

Biodiversity is the variety of life produced by evolution.

  • Speciation creates new species over time.
  • Organisms are grouped by taxonomy (domain to species).
  • Biodiversity supports ecosystem stability.
  • Extinction and human activity reduce biodiversity.

6Identify structures and functions of plant and animal systems

20% of exam

Multicellular organisms have organ systems with specific jobs.

  • Animal systems include digestive, circulatory, respiratory, and nervous.
  • Plant systems handle transport (xylem/phloem), photosynthesis, and reproduction.
  • Systems work together to maintain life.
  • Structure relates closely to function.

7Describe the principles of ecology

10% of exam

Ecology studies interactions between organisms and their environment.

  • Energy flows through food chains and webs (producers → consumers → decomposers).
  • Nutrient cycles (carbon, nitrogen, water) recycle matter.
  • Populations interact through competition, predation, and symbiosis.
  • Ecosystems balance biotic and abiotic factors.

Member-written study notes, not official HOSA competition material. Topic titles and exam weights come from the official Biology (ATC) guidelines.