Animal Form and Function

Radial Symmetry

The body is shaped like a pie or cylinder. Any slice through the central axis divides the animal into mirror images.

Bilateral Symmetry

The body has a central longitudinal plane that divides the animal into two equal but opposite halves (left and right).

Coelom

Fluid filled body cavity

Coelomate

The cavity is completely lined by tissue derived from the mesoderm. Internal organs are suspended by mesentery.

Pseudocoelomate

The cavity is formed from the mesoderm and endoderm. It is not fully lined by mesoderm.

Acoelomate

Animals that lack a body cavity. The space between the digestive tract and outer body wall is filled with solid tissue (mesoderm).

Diploblastic

Two layers (Ectoderm and Endoderm). Found in radially symmetrical animals.

Triploblastic

Three layers (Ectoderm, Mesoderm, and Endoderm). Found in all bilaterally symmetrical animals.

Segmentation

The division of the body into repetitive parts (like in earthworms or the vertebral column in humans), which allows for greater flexibility and specialization of body parts.

Hydrostatic Skeleton

A skeleton consisting of fluid held under pressure in a closed body compartment. Muscles change the shape of the fluid-filled compartments to create movement. (e.g., Earthworms, jellies).

Exoskeleton

A hard encasement deposited on the surface of an animal. It provides protection and points for muscle attachment but must be shed (molted) for the animal to grow. (e.g., Insects, crabs).

Endoskeleton

A hard skeleton buried within the soft tissues of an animal. It grows with the animal and can consist of cartilage, bone, or both. (e.g., Humans, fish, birds).

Ectoderm

gives rise to the epidermis of the skin (and its derivatives like hair/glands) and the entire nervous system.

Mesoderm

gives rise to the skeletal system, the muscular system, the circulatory system, and the dermis of the skin.

Endoderm

gives rise to the epithelial lining of the digestive tract and the respiratory system (lungs/gills).

Totipotent

Cells that can differentiate into any cell type in the body, including extra-embryonic tissues like the placenta. (e.g., Zygote).

Pluripotent

Cells that can differentiate into any of the three germ layers (ecto, meso, endo) but cannot form extra-embryonic tissue. (e.g., Embryonic stem cells).

Multipotent

Cells that can develop into more than one cell type, but are limited to a specific family or lineage. (e.g., Adult stem cells like bone marrow cells).

Unipotent

Cells that can only produce one cell type—their own—but have the property of self-renewal.

Cell Type

The basic unit of life, specialized for a particular function (e.g., a neuron or a red blood cell).

Tissue Type

A group of similar cells that work together to perform a specific function.

Organ

A structure composed of different types of tissues that work together to carry out a complex task (e.g., the heart or stomach).

Organ System

A group of organs that cooperate to perform major body functions (e.g., the circulatory system).

Physiology

The study of the physical and chemical processes and functions of living organisms and their parts.

Epithelial Tissue

Covers outside of organ, or lines inner surface of organs. Simple for absorption, stratified for protection (skin, intestine lining)

Connective Tissue

Sparse populations of cells scattered through an extracellular matrix. loose, dense(cartillage), fluid(blood), supporting(bone)

Muscle Tissue

Tissues responsible for nearly all types of body movement. Cells contain filaments of actin and myosin. (Skeletal muscle; cardiac muscle; smooth muscle -lines intestines.)

Nervous Tissue

Tissue that senses stimuli and transmits signals throughout the animal. Neurons (nerve cells), Glia (support cells)

Villi

Finger-like projections in the lining of the small intestine, vastly increase the surface area available for nutrient absorption into the blood.

Alveoli

Tiny, grape-like air sacs in the lungs that provide SA for oxygen and CO2 to diffuse

Homeostasis

The maintenance of a relatively constant internal environment despite fluctuations in the external environment.

Physiology & Homeostasis

Physiology is essentially the mechanism of homeostasis; it will kick in to maintain homeostasis

Set Point

The specific value or range at which a physiological variable (like body temperature or blood glucose) is optimally maintained.

Negative Feedback

A change in a variable triggers a response that counteracts the initial change, bringing the variable back toward the set point.

Sensor (Receptor)

Detects a change in the internal or external environment (a stimulus). Senses the current state.

Integrator (Control Center)

Processing center (often the brain or an endocrine gland) that compares incoming data from sensor to set point. It decides if a response is necessary.

Effector

A muscle, gland, or organ that carries out the response dictated by the integrator to return the variable to the set point.

Radiation

Heat transfer without direct contact. (basking)

Evaporation

Phase change from liquid to gas causes heat loss (sweating)

Convection

The transfer of heat by the movement of air or liquid past a surface. (wind on skin)

Conduction

The direct transfer of heat between objects in direct contact with each other. (sitting on hot thing)

Ectotherm

Uses external sources of heat

Endotherm

produces heat metabolically

Homeotherm

keeps body the same temp, controls body temp

Poikilotherm

fluctuating temp that approximates external temp, cannot control body temp

Countercurrent Heat Exchange

An arrangement of blood vessels in which fish or mammals move heat from warm arteries (flowing from the core) to cold veins (flowing from the extremities).

Centrioles

organizing the mitotic spindle during animal cell division, specific to animals

Lysosomes

break down waste, specific to animals

Flagella

hair like, used for movement, specific to animals

Extracellular Matrix

network of proteins and carbos between cells, specific to animals