8th Grade Life Science Final – Study Guide Answers 1. The correct pairing of the nitrogen bases of DNA are Adenine with Thymine and Guanine with Cytosine 2. The basic structure of the DNA molecule is a double helix 3. This is an example of the stages of mitosis 4. Incomplete dominance is a type of inheritance when two different alleles show up in the offspring. The offspring is not like either one of the parents. For example the black rooster and the white hen having black and white feathered chicks. 5. The correct order for the classification of organisms from the most basic category to the most complex is Domain, Kingdom, Phylum, Class, Order, Family, Genus and Species. 6. The physical expression of a trait is a phenotype. 7. The synapse is the junction where the axon can transfer an impulse to the dendrites of the next neuron. 8. The action of an organism as a result of a stimulus is called a response. 9. The process of producing new identical cells is called mitosis. 10. The “brain” of the cell is the nucleus. 11. Biology is the study of all living things 12. A habitat is the place where an organism lives and its needs are met. 13. Competition is the struggle between organisms to survive in a habitat with limited resources. 14. Adaptations occur when an organism has traits that help it survive better when its habitat changes. 15. The squirrel population would decrease if a late frost kills all of the acorns and other nuts in an ecosystem. 16. Limiting factors are environmental factors, like food, water, space, or weather that keep a population from growing. 17. Artificial selection is when humans breed organisms to produce desired results. For example, farmers cross pollinate large strawberry producing plants to grow large strawberries. 18. Three biotic factors in an ecosystem - Any living thing within an ecosystem like trees, beetles, fish, birds, etc. 19. RY Ry rY ry RRYY RRYy RrYY RrYy RY Ry RRYy RRyy RrYy Rryy rY RrYy RrYy rrYY rrYy ry RrYy Rryy rrYy rryy 21. In an energy pyramid the producers have the most available energy and organisms. 22. A food chain is a series of events in which one organism eats another and obtains energy. A food web is many overlapping food chains within an ecosystem. 23. Humans have 46 chromosomes 24. An example of population is any number of one species living in an area. An example would be 5 white tailed deer living in 10 acres of forest land. 25. The biological process of perspiration is called homeostasis. 26. Nitrogen fixing is the process changing free nitrogen into a usable form of nitrogen. The higher the animal in a food chain in a particular ecosystem, the greater the concentration of toxins found in the animal’s body. 27. Inheritance of traits is determined by a pair of factors passed down from both parents. 28. If there was 100,000 units of energy available to grass, then there would be 10,000 units of energy available to the grasshopper because only 10% of the energy is passed on from one trophic level to the next.