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General Biology Unit 3 Study Guide

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  • What is the significance of the Cambrian explosion in animal evolution?

    The Cambrian explosion was a brief period (~535–525 million years ago) when many present-day animal phyla first appeared, including the emergence of large, hard-bodied animals.

  • Define 'bilaterian' animals.

    Bilaterians are animals with bilateral symmetry and three germ layers, representing a major clade in animal evolution.

  • What are the key traits of chordates?

    Chordates have a notochord, dorsal hollow nerve cord, pharyngeal slits or clefts, and a muscular post-anal tail at some stage of development.

  • What distinguishes amniotes from other tetrapods?

    Amniotes have an amniotic egg with specialized membranes, including the fluid-filled amnion, protecting the embryo; includes mammals, birds, and reptiles.

  • Describe the difference between negative and positive feedback.

    Negative feedback counteracts a change to maintain homeostasis, while positive feedback amplifies a change, often driving a process to completion.

  • What is homeostasis in animals?

    Homeostasis is the steady-state physiological condition of the body, maintaining variables like temperature and solute concentration within set points.

  • Define regulator and conformer in terms of internal conditions.

    A regulator maintains internal conditions despite external changes; a conformer’s internal conditions change with the environment.

  • What are the four major categories of animal tissue?

    Epithelial (lining), connective (support), muscle (movement), and nervous (signal transmission) tissues.

  • What is the role of the endocrine system?

    The endocrine system uses hormones secreted by glands to regulate internal processes and maintain homeostasis over longer timescales.

  • How does the nervous system differ from the endocrine system?

    The nervous system provides fast, targeted communication via neurons, while the endocrine system uses slower, widespread hormonal signaling.

  • What is thermoregulation and how do endotherms and ectotherms differ?

    Thermoregulation is maintaining internal temperature; endotherms generate heat metabolically, ectotherms rely on external heat sources.

  • Describe the four stages of food processing in animals.

    Ingestion (eating), digestion (breaking down food), absorption (nutrient uptake), and elimination (waste removal).

  • What are essential nutrients?

    Substances animals cannot synthesize and must obtain preassembled from their diet, including essential amino acids, fatty acids, vitamins, and minerals.

  • Compare open and closed circulatory systems.

    Open systems bathe organs directly with hemolymph; closed systems confine blood to vessels, allowing more efficient transport.

  • What are the three main types of blood vessels and their functions?

    Arteries carry blood away from the heart, capillaries enable exchange with tissues, and veins return blood to the heart.

  • Explain single vs double circulation.

    Single circulation passes blood once through the heart per circuit (e.g., fish); double circulation has separate pulmonary and systemic circuits (e.g., mammals).

  • What is the cardiac cycle?

    The alternating contraction (systole) and relaxation (diastole) phases of the heart that pump blood through the body.

  • What is countercurrent exchange and its biological importance?

    Countercurrent exchange is the transfer of substances or heat between fluids flowing in opposite directions, maximizing diffusion efficiency, e.g., in fish gills.

  • Describe the role of insulin and glucagon in blood glucose homeostasis.

    Insulin lowers blood glucose by promoting uptake and storage; glucagon raises blood glucose by promoting glycogen breakdown and release.

  • What is osmoregulation and why is it important?

    Osmoregulation controls solute concentrations and water balance to maintain cellular function and homeostasis.

  • List the four steps of the excretory process.

    Filtration, reabsorption, secretion, and excretion, which together remove wastes and regulate body fluids.