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Ch 25 What Is An Animal
25.1. Typical Animal Characteristics
A. Characteristics of Animals – Eukaryotic, multicellular, _________________, heterotrophic organisms
1. Methods for obtaining food vary – mobile animals have the ability to seek found whereas sessile
animals rely on food coming to them (ex: water brings food to barnacles)
a. _________________ – organisms that don’t move from place to place
2. Animals must digest food - animals are _________________ and must digest food. Most animals
have a _________and ___________, some only have __________body opening.
3. Animal cell adaptations – animals have specialized _______________to carry out metabolic functions
B. Development of Animals – most animals develop from a single, fertilized egg called a zygote.
1. _________________ –occurs when
sperm fertilizes an egg. It may be
internal or external
2. Cell division – zygote divides by mitosis
a. _________________ – a hollow ball of cells
3. Gastrulation - blastula folds inward
a. _________________ – a structure
made of two layer of cells with an
opening at one end
b. _________________ - the layer of
cells on the outer surface of the gastrula
c. _________________ – the layer of
cells lining the inner surface
4. Formation of the mesoderm – found in the middle layer
of the embryo
a. _________________ - the third cell layer found in the
developing embryo between the ectoderm and the endoderm
b. protostome - an animal with a _________ that develops
from the opening in the gastrula (ex: earthworms/insects)
c. _________________ – an animal in which the mouth
develops from cells elsewhere on the blastula (ex: fish,
birds and humans)
5. Continued growth and development – In some animals, the _________________ develops into a
_________________ which is different from the adult version. (ex: echinoderms and insects)
6. Forming an adult animal – eventually, all juveniles reach sexual maturity and the life cycle can repeat
25.2. Body Plans and Adaptations
A. What is Symmetry?
a. _________________ – a balance in proportions of an object or
1. _________________ in a sponge – an animal with an irregular
shaped body (ex: sponge)
2. Radial symmetry in a hydra
a. _________________ _________________ – can be divided
along any plane through a central axis into roughly equal halfs
3. Bilateral symmetry – ex: any organism with a head
a. _________________ _________________ – can be divided
down its length into similar right and left halves that form mirror images.
d. ______________
– back surface
b. _________________ – head
c. ____________
– tail end
e. _________________ –
belly surface
B. Bilateral Symmetry and Body Plans
1. Acoelomate flatworms have no body cavities – “A” = without, “coelom” = body cavity
a. _________________ – 3 cell layers – ectoderm, endoderm, mesoderm - but no body cavity
2. Pseudocoelomates have a body cavity – “pseudo” = false. Body cavity develops between the
endoderm and the mesoderm
a. _________________ – a fluid-filled body cavity partly lined with mesoderm
3. The coelom provides space for internal organs
a. _________________ – a fluid-filled space that is completely surrounded by mesoderm
C. Animal Protection and Support
a. _________________ – a hard, waxy covering on the outside of the body that provides a framework
for support
b. _________________ – an internal skeleton that provides support inside an animal’s body
c. _________________ – an animal that does not have a backbone
d. _________________ – an animal with a backbone