Producer Alga is A plant and produces food for other organisms <span />
a. A shared ancestral character.
Explanation:
The condition of birds and mammals having four limbs is a shared ancestral character because the structure of the limbs are similar in both the cases.
The forelimbs of the bird are modified into wings to aid flying.The hind limbs are modified into feel and claws.
These are homologous structures to the hands and feet in mammals.
That means they have a common origin, and hence are shared ancestral character.
This is an effective strategy because different phases do not compete for food.
For example for the case of Jelly fish, After a brief period floating about in surface waters like planktons, the larvae then settles to the sea floor, attaching themselves to one end. They then develop to polyps and begin to feed and grow. In spring the polyps bud iff immature jellyfish known as ephyra larvae which then grow to mature jellyfish.