The Chatham Island robin is a small endangered bird found in scrub forests off the coast of New Zealand. The robin is preyed upo
n by introduced species such as cats and rats. In 1980, the population decreased to only 5 individuals and every individual today is a descendant of a single female. Which of the following is best illustrated in the decline of the Chatham Island robins? 1. Carrying capacity
2. Population bottleneck
3, Population overshoot
4. Type I survivorship
A Population bottleneck is a term used to refer to an event that causes the population of a species to reduce in very large numbers. Such an event can be environmental disasters like famine, the overhunting of a species or the destruction of its habitat.
In the case of the Cha-tham Island Robin, the bottleneck event must have been the introduction of cats and rats which then went on to hunt the birds to near extinction.
The yolk sac functions to form blood cells in early development (embryonic phase) for nourishment of the embryo and early fetus. Towards the end of the 1st trimester, the yolk sac disappears and the placenta takes over for the fetus.
