unit 8 chapter 25 what is an animal?. characteristics of animals 1) they are multicellular 2) they...
TRANSCRIPT
Characteristics of Animals
1) They are multicellular
2) They are heterotrophs (consumers) Motility = most animals use locomotion to find
their food sources
Sessile = organisms that are permanently attached
(don’t spend much energy to obtain food)
Sponges are sessile animals
Characteristics of Animals
3) They injest their food 4) They have specialized cells, tissues,
organs, & systems Ex: the complex digestive tract of the earthworm
Characteristics of Animals 5) They have similar stages of development:
Blastula Fluid-filled ball formed
from many cell divisions Gastrula
Blastula folds inward to form two layers
Gastrulation
Formation of a cavity of two or more layers with an opening at one end
1) Ectoderm = outermost layer
2) Endoderm = innermost layer
Higher animals have a third, middle layer:
3) Mesoderm = develops into muscles, etc
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2
3
Symmetry
the arrangement of body structures
1) Radial symmetry Can be divided along any
plane, through a central axis, into roughly equal halves
2) Bilateral symmetry Can be divided down its length into similar
right & left halves
Has a definite front (anterior,) rear (posterior), top (dorsal,) and belly side (ventral)
Body plans
Pseudocoelomates
A fluid=filled body cavity only partially lined with mesoderm
Ex: Roundworms
Body plans Coelomates Has a fluid-filled body cavity completely
surrounded by mesoderm Ex: segmented worms & all higher animals
Animal Diversity
Invertebrates Animals without
backbones Often having
exoskeletons outside their body for framework & support