Chapter 7 – Simple Animals
Scientists have discovered and classified over 1.5 million living things
- of this, about 1 million are animals
Traits of Animals
1) Consumers (they can’t make their own food)
2) Most can move from place to place
3) Are multicellular organisms
- put into one of two groups
1) vertebrates = animals with a backbone
2) invertebrates = animals without backbones
4) Most animals have symmetry = arrangement of body parts around a center
point or along a center line
- two types:
1) radial symmetry = the body parts are arranged in a circle around a
center point
2) bilateral symmetry = the body can be divided lengthwise into two equal
sides, a right and left side
Classifying Animals
- animals are classified based on specific traits
- there are nine major phyla (groups) of animals
1) Sponges (5,000)
2) Stinging-Cell Animals (11,000)
3) Flatworms
4) Roundworms
(26,000)
5) Segmented Worms
6) Soft-Bodied Animals (80,000)
7) Jointed-Leg Animals (826,000)
8) Spiny-Skin Animals (5,000)
9) Chordates – Vertebrates (47,000)
- 8 of the 9 phyla (groups) are invertebrates
Sponges
- simplest type of invertebrates
- have pores (tiny openings)
- have no definite shape or color
- live attached to rocks and obtain food through filter feeding
- reproduce sexually or asexually
Stinging-Cell Animals
= animals with stinging cells and hollow, saclike bodies that lack organs
- examples: hydras, corals, sea fans, jellyfish, sea anemones
- have only one opening called the mouth
- many attach themselves to structures like rocks with a part called a disc
- acts like a suction cup
- feed by ways of tentacles with poison darts on the end
- tentacles catch food and pull it into the mouth
- have radial symmetry
- have muscles and nerve cells that allow them to move from place to place
Flatworms
- the simplest type of worms
- most are parasites
- absorb food that the host has already digested
- example: tapeworm
- lives in the intestine of almost any kind of vertebrate
- form cysts in the muscles = a young worm in a protective coating
- not common in the United States due to sewage treatment and meat
inspection
- should cook meat thoroughly to kill tapeworms in meat
- example: planarian
- not a parasite
- less than one cm long
- mouth is near the middle of the underside of its body
- has eyespots with nerve cells that detect light
Planarian (Internal & External Anatomy)
Roundworms
= worms that have long bodies with pointed ends
- many are parasites
- live in great numbers in the soil
- example: hookworm
- enter the body through the skin of the feet
- from there they move to the intestine
- can rupture the intestinal wall and block
ducts in the body
Male and Female Roundworms in Intestine
Segmented Worms
= worms with bodies divided into sections called segments
- example: leech
- is a parasite
- used in medicine to drain excess blood
- example: earthworm
- body has layers of muscles to help it move
- small bristles called setae that help it move through the soil
- these make it hard to pull a worm from the ground backwards
- take in soil through its mouth
- the soil itself is not food but the things inside it are (dead leaves,
insects, seeds)
- enrich the soil and loosen it, helping plants grow
Internal & External Anatomy of an Earthworm
Soft-Bodied Animals
= animals with a soft body that is protected by a hard shell
- the body is protected by a thin, fleshy tissue called the mantle
- the mantle makes the shell
- have a muscular foot for moving from place to place
- each type has a different looking foot with a different job
- 3 Classes of Soft-Bodied Animals
1) Snail and Slugs
- two pairs of tentacles on the head have sense organs
2) Clams, oysters, and scallops
- have two shells
- foot is like a shovel that is used to burrow into the ground
3) Octopus and Squid
- well-developed eyes
- rapid swimmers by shooting a jet of water
Snail (External Anatomy)
Clam (Internal Anatomy)