Characteristics of life according to Biologists
Biologists’ opinions may vary but it is generally agreed
that the following characteristics provide a good basis
of what is needed to qualify something as alive:
1.
2.
3.
4.
5.
6.
Responds to stimuli
Grows and develops
Reproduces
Uses energy (AKA metabolizes)
Is made of cells
Evolves
Characteristics of animals
1. Multicellular and eukaryotic
2. Skeleton (internal or external)
- what is equivalent in plants and fungi?
3. Start as a zygote, develop into embryo
- what is the difference?
4. Consumers
5. Motile
6. Diploid
How do we classify animals?
● Symmetry
○
○
○
Asymmetrical - no symmetry
Radial symmetry- body parts arranged in a circle around a central point
Bilateral symmetry - draw a line down middle and the two halves match
How do we classify animals?
● Gut (digestive tract)
○ No gut - food
digested within cells
○ Incomplete gut - AKA
sac-like gut. one
opening
○ Complete gut - two
openings: mouth and
anus
How do we classify animals?
● Body cavity
○ No body cavity
○ Body cavity - space to house and protect gut.
filled with fluid and digestive organs
● Skeleton
○ Endoskeleton - vertebrates
○ Exoskeleton - invertebrates
○ Hydrostatic - liquid pressure
Other ways to classify:
● Tissues
● Segmentation
● Proto- versus
deuterostome