CRUSTACEANS (THE CRAB)

Question 1

explain Body Structure

Answer 1

crabs have diff shapes and sizes. The body of crab can be divided into cephalothorax & abdomen crabs have 10 legs & front pairs are pinchers 2 antennae & 2 eyes on stalks. the crab main defense is its hard exoskeloton.

Question 2

explain Movement

Answer 2

crabs have long legs have to move sideways .if they walk forward they trip over own feet. most crabs have paddle shaped limbs to swim

Question 3

explain Nutrition and Feeding

Answer 3

omnivores .
strong digestive system
easly digest algae fungi molluscs bacteria worm shrimp
crabs need protein aswell vitamins
crabs mouthpiece consists of alot pairs jaws each with seperate function
make sure food held in place minced and pushes into mouth
respiration

Question 4

explain Gaseous Exchange

Answer 4

resemble fish in use of gills to exchange gasses
gills are feathery structure stay moist for respiration to occur
oxygen dissolves in moisture be absorbed through a thin membrane & transported to rest of body. many crab species can survive on land for land for a long time because they have gill chambers

Question 5

explain Maintaining Water Balance

Answer 5

crabs have a hard exoskeleton prevents water from being absorbed / escaping through the body external covering water most important function in crabs is that it enables respiration

Question 6

explain Reproduction

Answer 6

reproduction of crabs differs from species to species. some lay up to 120 000 eggs. laid low water are mostly carried by mother. then rleases the egg in stream where enough plankton for little crabs to feed on. when crab are big enough their exoskeleton have hardened, the stream takes them back to the bank of the stream where they live between the rock and plantlife

Question 7

explain Senses

Answer 7

• 2 compound eyes on stalks cannot focus well they can observe movement and colour
• crabs antennae called chemoreceptors used to detect observe smell and taste enabling crab to find food
• despite their hard exoskeleton, crabs have a well-develope sense of touch. not only are their bodies and leg sensitive, fine hair on surface of their pincers is also sensitive to vibrations in the water

Question 8

explain Crustaceans In The Ecosystem

Answer 8

important role in most food chains. from smallest species that serve as a source of food many sea animals to the largest Tasmanian Giant crab whose eggs serve as a source of food for various coastal birds, they all play an important role in ecosystem. most crustaceans have ability to drop or shed their legs when attacked . these legs will then grow after a certain period of time