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Chapter 26-1 Notes
Basic Characteristics of Animals
I. Kingdom Animalia
A. Characteristics of animals
a. Multicellular
b. Heterotrophic
c. Eukaryotic (cells have nucleus)
d. No cell walls
e. 1.5 million species of animals (35 different phyla)
f. 95% of animals are invertebrates (no backbone)
B. Animals carry out the following functions:
a. Feeding - eating
b. Respiration – take in oxygen and give off carbon dioxide
c. Circulation – flow of nutrients, oxygen, etc through body
d. Excretion – get rid of waste (ex: ammonia)
e. Response – respond to environment; some have nerve
cells
f. Movement – many animals have muscles that provide
movement of body and some internal organs
g. Reproduction – most reproduce sexually - this maintains
genetic diversity; some reproduce asexually – this allows
animals to increase their numbers rapidly
C. Homestasis - all the body systems work together to create a
balance in the organism
D. Feedback Inhibition – the result of a process stops or limits that
process
a. Example: panting in dogs: If dog is hot then they will pant to
cool the body; as body temperature lowers, the panting will
slow or stop
E. Early Development in Animals
a. Animals begin as a zygote – fertilized egg that becomes a
developing embyro
b. Embryo development – 3 main tissue layers:
1. Endoderm – (innermost layer); becomes digestive
tract and respiratory system
2. Mesoderm – (middle layer) ; becomes muscles,
circulatory system, reproductive and excretory
systems
3. Ectoderm – (outermost layer); becomes sense
organs, nerves, and outer skin layers
F. Body Shape
A. Radial Symmetry – body parts extend from a central point
B. Bilateral symmetry – body can be divided into 2 equal
halves; usually have left and right side, and front and
back
Body Symmetry
Radial Symmetry
Bilateral Symmetry
Asymmetric
Evolutionary Relationships among Major Groups of Animals