b. euglenoids.
c. plasmodial slime molds.
d. water molds.
c. It is prokaryotic.
d. It is autotrophic.
Natural casts
Natural casts are fossils that consistof minerals that are filled in an open mold of an organism. This type of castsis made when minerals are deposited in the mold. Casts can also be syntheticallyproduced when the molds are filled with synthetic material such as latex.
extinction would lead to the extinction of other forms of life. A keystone species helps to
support the ecosystem of which it is a part.
An example of what can happen when a keystone species is removed occurred when fur
hunters eliminated sea otters from some Pacific Ocean kelp beds. Otters eat sea urchins,
which eat kelp. With its major predator gone, sea urchin populations exploded and
consumed most of the kelp. Fish, snails, and other animals associated with the kelp beds
disappeared.
The grizzly bear is another example of a keystone species. Grizzlies transfer nutrients
from the ocean ecosystem to the forest ecosystem. The first stage of this transfer is
performed by salmon that swim up rivers, sometimes for hundreds of miles. Salmon are rich
in nitrogen, sulfur, carbon, and phosphorus. The bears capture the salmon and carry them
onto dry land, scattering nutrient-rich feces (wastes) and partially eaten salmon carcasses.
It has been estimated that the bears leave up to half of the salmon they harvest on the
forest floor.
Which sequence best represents the feeding relationships in a kelp ecosystem that has not been disturbed
by humans?
(1) sea urchins → kelp → fish (3) kelp → sea otters → sea urchins
(2) kelp → sea urchins → sea otters (4) sea urchins → snails → kelp
The correct sequence displaying the feeding relationships in an undisturbed kelp ecosystem is: kelp → sea urchins → sea otters. Kelp serves as a food source for sea urchins, which in turn are consumed by sea otters.
The sequence that best represents the feeding relationships in a kelp ecosystem that has not been disturbed by humans is (2) kelp → sea urchins → sea otters. In an undisturbed ecosystem, the kelp, being a producer, forms the base of the food chain. Secondly, the sea urchins, as primary consumers, feed directly on the kelp. And finally, the sea otters are secondary consumers that prey on the sea urchins, maintaining the balance in the ecosystem.
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