Chapter 21 - Biology

sessile

organism permanently attached to one place

cnidocytes

nematocyst-containing stinging cell on a cnidarian’s tentacle

nematocysts

capsule whose threadlike tube contains poison and barbs and is discharged when prey touches a cnidarian.

hydrostatic skeleton

fluid within a closed space that provides ridged support for muscles to work against.

mantle

membrane that surrounds a mollusk’s internal organs.

radula

rasping tongue-like organ with rows of teeth that many mollusks use in feeding

setae

tiny bristle that digs into soil and anchors an earthworm as it moves forward.

thorax

middle body region of an arthropod consisting of three fused main segments that may bear legs and wings

abdomen

in invertebrate, posterior body region that contains segments, digestive structures, reproductive organs, and bears additional legs; in vertebrates, part of body that is between the diaphragm and pelvis

appendages

a structure such as a leg or an antenna that grows and extends from the body or body covering.

water-vascular system

system of fluid-filled, closed tubes that allow echinoderms to control movement and get food

Chordates

animal of the phylum Chordata having a dorsal tubular nerve cord, a notochord, pharyngeal pouches, and a postanal tail at some point in its development.

Invertebrate

chordate without a backbone

Amnion

fluid-filled membrane that surrounds and protects a developing embryo

Mammary glands

mammalian gland that produces and secretes milk to nourish developing young

fins

a paddle-shaped structure used for balance, steering, and propulsion

endotherms

organism that generates its body heat internally by its own metabolism

placenta

in most mammals, the specialized organ that provides food and oxygen to the developing young and removes its waste

sternum

the breastbone in vertebrates; in birds, bone to which flight muscles are attached

scales

small, flat, platelike structure on the skin surface of most fishes

feathers

specialized outgrowth of the skin of birds used for flight and insulation

amniotic egg

egg that provides a complete environment for the developing embryo with a yolk sac for nutrition, protective internal membranes and fluid, and a protective outer shell

contour feathers

feathers that cover the body, wings, and tail of a bird

monotremes

mammals that lay eggs

behavior

any way that an animal responds to a stimulus

innate behavior

genetically based

fixed action pattern

an animal that carries out a specific set of actions in the same order in response to a stimulus

learned behavior

behavior that results from an interaction between genetically based behaviors and past experiences

habituation

a decrease in an animals response after repeatedly being exposed to a stimulus

classical conditioning

an association is made between two different kinds of stimuli

operant conditioning

learning to associate a response to a stimulus with a reward or punishment

imprinting

learning that occurs within a specific time period in an animal’s life and is permanent

cognitive behavior

an animal solves a problem

agonistic behavior

threating or combative behavior between two members of the same species

dominance hierarchies

ranking system in which the top-ranked animal gets access to resources without conflict from others in the group

territorial behaviors

competitive behavior in which an animal tries to adopt and defend a physical area

foraging behaviors

ecological behavior that involves finding and eating food

migratory behaviors

seasonal movement of a group of animals to a new location for feeding and breeding

circadian rhythm

cycle that occurs daily, such as sleeping and waking

language

auditory communication in which animals use their vocal organs to produce sounds with shared meaning

courting beahviors

species-specific series of movements or sounds used to attract a mate

nurturing behaviors

caretaking behavior that a parent provides to its offspring during early stages of development

altruistic behavior

self-sacrificing behavior that benefits another individual

natural selection

traits that result in the greatest number of offspring eventually become the most common trait in the population

marsupials

offspring that develop in a pouch

placental mammals

placenta that provides food and oxygen