|
|
 |
SALISH SEA
A Handbook For Educators
Sample Activities
Teacher's Notes
Kelp Crab
Kelp Crabs begin their life as eggs in a little flap that unfolds
from their mother's abdomen or belly. Depending on conditions, the
female can reproduce all year, so look for eggs on the female even
in the winter. After a courtship, the male deposits sperm and fertilizes
the female's eggs. The abdomen acts like a spongy cradle for as many
as two hundred thousand eggs. The mother carries her eggs around with
her for about two weeks until they hatch as a tiny pre-adult stage
called zoea. These crab larvae drift on the tide and form part of
the plankton soup. Over several months they go through rapid changes
and end up looking as crab-like megalops. At this stage, they settle
down to the sea floor and start their adult lives. As the crab grows
it sheds or "molts" its hard shell. This molted shell often
looks like a dead crab at the beach. Juvenile crabs molt as many as
8 times a year.
The ocean is where life began. More than two billion years ago, there evolved single-celled algae similar to the plant plankton that form the basis of life in today's oceans. Some of the ocean residents have a very long history: jellyfish and sea worms, for example, were living in the sea at least 600 million years ago. Fish appeared approximately 420 million years ago, while whales are newcomers to the ocean, having moved into the marine environment from the land only about 60 million years ago.
Each kind of plant and animal has its own life cycle. By studying the life cycles of marine plankton and selected marine animals, children can observe the characteristics of living organisms. Three natural events can be observed at the seashore, in a classroom aquarium, or researched in books: birth, growth, and death. At the seashore, children may notice crabs or gulls mating, a female crab with her abdomen extended with eggs, and the death and decay of gulls, sea stars and seaweeds. Each experience with living organisms should increase the child's awareness of the differences between plants and animals, and non-living things. At the same time they should develop some understanding of how marine plants and animals interact with one another and with the water, nutrients, and sun in the vast network of relations that constitute life.
Kelp Crab Life Cycle
©
Parks Canada |
64 |
(Seal's Lullaby
is song #8 on the Salish Sea CD - See page 18 for Music activities)
|
|
