Sea urchins belong to the echinoderm phylum. Adult sea urchins have spines that extend outward from their exoskeleton, but as larvae, the sea urchins have only an exoskeleton made from spicules. The spines offer protection against predators. The population size of sea urchins is low in relation to the carrying capacity of the area. As a result, the sea urchins are Multiple choice question. A) r-strategists that allocate much energy toward parental care. By-strategists that allocate energy to producing many young. C) density-independent, because there is plenty of energy. D) irruptive, because their numbers crash quickly.

Complete question:

Sea urchins belong to the echinoderm phyla. Adult sea urchins have spines that extend outward from their exoskeleton, but as larvae, the sea urchins have only an exoskeleton made from spicules. The spines offer protection against predators. Sea urchins typically spawn near the surface. Males release sperm into floating plankton, then female urchins release between eight and 20 million eggs in the same area. The jelly-like coating on the eggs attracts the sperm, and when the two meet, they create an embryo that starts dividing into new cells within minutes.

Based on the information the population size of sea urchins is low in relation to the carrying capacity of the area. As a result, the sea urchins are

A) r-strategists that allocate much energy toward parental care.

B) r-strategists that allocate energy to producing many young.

C) density-independent because there is plenty of energy.

D) irruptive, because their numbers crash quickly.

B) r-strategists that allocate energy to producing many young.

Explanation:

According to the given information, this species expresses survival curve type III, characteristic of r-strategists. Males and females release many gametes into the sea. If these gametes get to meet, they produce the embryo that starts developing. But there are high chances for these new organisms to die. Significant mortality during the early stages of life is expected for the species. The few individuals that manage to reach the later life stages, getting to survive, usually have a long life. These species produce many gametes to release, which results in the production of many offspring simultaneously. However, adult individuals provide no parental care. Their success in reproduction depends on the number of surviving descendants.

We might also mention that the population size is under the carrying capacity. r-strategist choose to live in areas with only a few individuals, where nitches are hardly occupied.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!