Hamilton - Honors Biology Chapter 27 Introduction to Animals

multicellular

made of more than one cell

eukaryotes

organisms whose cells have a nucleus

lack cell walls

animal cells do nor have rigid outer walls like plants or fungi

ingestive heterotrophs

take in food and digest it internally

store sugar as glycogen

animals store excess glucose as glycogen, mainly in liver and muscles

motile

able to move

sessile

unable to move; attached to a surface

invertebrates

animals without a backbone

vertebrates

animals with a backbone

animal diversity

about 35-40 phyla; includes a wide variety of body plans

zygote

fertilized egg

embryo

early stage of development after the zygote begins to divide

tissues

groups of similar cells working together

symmetry

arrangement of body parts around a central point or axis

asymmetry

no symmetry; body can't be divided into equal parts (e.g., sponges)

radial symmetry

body parts arranged around a central axis (e.g., cnidarians, echinoderms)

bilateral symmetry

body can be divided into mirror-image halves on one plane

cephalization

concentration of sense organs and brain in the front (anterior) of the body

body segmentation

body made of repeating sections

dorsal

upper or back side

ventral

lower or belly side

anterior

front or head end

posterior

rear or tail end

cleavage

rapid cell division of a zygote

blastula

hollow ball of cells formed after cleavages

blastocoel

fluid-filled cavity inside the blastula

gastrulation

process where the blastula forms inward to form a gastrula

gastrula

multilayered embryo with an opening called the blastopore

blastopore

opening that forms during gastrulation

protostomes

animal where the blastopore becomes the mouth (e.g., worms, mollusks)

deuterostomes

animals where the blastopore becomes the anus (e.g., echinoderms, chordates)

ectoderm

outer layer; forms skin, nerves, sense organs

endoderm

inner layer; forms digestive tract lining, liver, lungs

mesoderm

middle layer; forms muscles and other organs

coelom

fluid-filled body cavity between the digestive tract and outer-body wall

acoelomates

animals with no body cavity (e.g., sponges, flatworms)

pseudocoelomates

have a body cavity not fully lined with mesoderm (e.g., roundworms)

coelomates

body cavity fully lined with mesoderm (e.g., annelids)

closed circulatory system

blood stays in vessels (e.g., annelids, vertebrates)

open circulatory system

blood flows freely in body cavity (e.g., arthropods, mollusks)

diffusion (no circulatory system)

used by simple animals like sponges and flatworms to exchange gasses and nutrients