Biology 2

Gastrulation

The process during early embryonic development where cells reorganize to form three primary tissue layers called germ layers: ectoderm, endoderm, and mesoderm.

Acoelomate

An organism with no body cavity, such as flatworms from the phylum Platyhelminthes.

Pseudocoelomate

An organism with a partially lined cavity, such as nematodes.

Coelomate

An organism with a fully lined body cavity (true coelom), examples include annelids, mollusks, arthropods, and chordates.

Ectoderm

The outer tissue layer that develops into the skin and nervous system.

Endoderm

The inner tissue layer that develops into the digestive tract and lungs.

Mesoderm

The middle tissue layer that develops into muscles, bones, and the circulatory system.

Radial Symmetry

A symmetry pattern that allows organisms to interact with the environment from all sides, beneficial for stationary animals.

Bilateral Symmetry

A symmetry pattern that allows for directional movement and better coordination, advantageous for active animals.

Cephalization

The concentration of sensory organs and brain at the front of the body, enhancing environmental detection during forward movement.

Segmentation

A biological feature that allows body parts to specialize and evolve independently, leading to improved movement and function.

Exoskeleton

A protective outer skeleton found in arthropods providing support and preventing water loss.

Endoskeleton

An internal skeletal structure, such as that found in vertebrates.

Hydrostatic Skeleton

A support structure seen in annelids, using fluid pressure to maintain shape.

Synapomorphies of Animals

Characteristics that define animals: multicellular, heterotrophic, no cell walls, specialized tissues, and undergo embryonic development.

Echinodermata

A phylum characterized by radial symmetry in adults, a water vascular system, and tube feet.

Amniotic Egg

An egg with protective membranes allowing reproduction away from water, crucial for terrestrial life.

Natural Selection

The process where variation, competition, and survival lead to evolution.

Exponential Growth

A type of population growth where resources are unlimited, leading to rapid increase.

Logistic Growth

A population growth model limited by carrying capacity (K), showing slow growth as it approaches limit.

Hermaphrodite

An organism that has both male and female reproductive organs.

Isolation Mechanisms

Factors causing speciation, can be geographic (physical barriers) or reproductive (behavioral or temporal differences).