39.1 Form, Function, and Adaption

• Biologists who study animal anatomy and physiology are studying adaptations-heritable traits that make individuals more likely to survive and reproduce in a certain environment than individuals that lack those traits.

• The most important constraint on adaptation, though, maybe trade-offs-inescapable compromises between traits.

• During mating, a male cricket produces a spermatophore, a packet of sperm surrounded by a large, gelatinous mass.

  • The male deposits the spermatophore on the female’s genital opening.

  • After mating, the female begins to eat the gelatinous mass.

• Phenotypic change in an individual in response to environmental fluctuations is referred to as acclimatization.

39.2 Tissues, Organs, and Organ System: How Does Structure Correlate with Function?

• A tissue is a group of cells that function as a unit.

• Nervous tissue consists of nerve cells, which are also called neurons, and several types of supporting cells.

  • Neurons transmit electrical signals, which are produced by changes in the permeability of the cell’ s plasma membrane to ions.

• Muscle tissue was a key innovation in the evolution of animals-like nervous tissue, it appears in no other lineage on the tree of life.

• The skeletal muscle attaches to bones and exerts a force on them when it contracts.

  • Skeletal muscle is responsible for most body movements.

  • It has long cells with a striated, or striped, appearance produced by an overlapping arrangement of proteins.

• Cardiac muscle makes up the walls of the heart and is responsible for pumping blood throughout the body.

  • The branching pa ern of cardiac muscle allows electrical signals to spread throughout all cells of the heart, resulting in their coordinated contraction and relaxation.

• Smooth muscle cells, which are tapered at each end, form muscle tissue that line the walls of the digestive tract and the blood vessels.

  • Contraction and relaxation of smooth muscle help move food through the digestive tract and regulate blood pressure.

• An organ is a structure that serves a specialized function and consists of two or more tissues; a gland is an organ at secretes specific molecules or solutions such as hormones or digestive enzymes.

• Connective tissues consist of cells that are loosely arranged in a liquid, jellylike, or solid matrix.

• An organ system consists of groups of tissues and organs that work toge er to perform one or more functions.

39.3 How Does Body Size Affect Animal Physiology?

• Metabolism is 1e sum of all chemical reactions that occur within an organism.

  • Given that metabolism requires energy, the metabolic rate is the overall rate of energy consumption by an individual.

• Because an individual’ s metabolic rate varies dramatically with its activity, the accepted convention is to report the **basal metabolic rate (BMR）**一the rate at which an animal consumes oxygen while at rest, with an empty stomach, under normal temperature and moisture conditions.

39.4 Homeostasis

• Homeostasis (literally, “ alike-standing”) is defined as stability in the chemical and physical conditions within an organism’s cells, tissues, and organs.

• Many organisms are able to regulate their internal conditions to actively maintain relatively constant internal conditions even when the environment fluctuates.

• For example, many aquatic animals do not maintain their body temperature above the ambient temperature because they would lose heat quickly to the surrounding water.

  • Instead, these animals conform to environmental conditions.

• Like the thermostat in a home heating system, each of these systems has a set point-a target range of values for the controlled variable.

• Homeostatic systems are based on negative feedback.

  • When negative feedback occurs, effectors return internal conditions to set-point values.

39.5 Thermoregulation: A Closer Look

• An animal that is an endotherm (“inner-heat”) produces adequate heat to warm its own tissues, while ectotherm (“outer-heat”) relies principally on heat gained from the environment.

• Homeotherms (“alike-heat”) keep their body temperature constant, while in poikilotherms (“varied-heat”), body temperatures rise or fall depending on environmental conditions.