Mastering Biology Chp. 25 HW

Which of the following is true of secondary endosymbiosis?

An organism containing an endosymbiont is engulfed by another organism and becomes an endosymbiont. This is a description of secondary endosymbiosis. In many cases secondary endosymbionts are surrounded by four membranes.

Which of the following is a correct statement about cellular slime molds?

Cellular slime molds form masses when food is scarce, but their cells remain separated. Cellular slime molds function almost like multicellular organisms when food is depleted. They form a multicellular mass that forms fruiting bodies.

Which of the following statements supports the hypothesis of an endosymbiotic origin of mitochondria?

Each mitochondrion has its own DNA molecule. The fact that mitochondria have their own DNA provides strong support for the hypothesis of an endosymbiotic origin of mitochondria.

Select the correct statement about photosynthesis by primary producers.

Photosynthetic protists and prokaryotes carry out the majority of the photosynthesis in aquatic communities. Scientists estimate that 30% of the world's photosynthesis is performed by aquatic protists. Photosynthetic prokaryotes contribute another 20%, and land plants are responsible for the remaining 50%. Read about the key roles that protists play in ecological communities.

How can the response of diatom populations to a drop in nutrient availability affect other organisms? Match the words in the left column to the appropriate blanks in the sentences on the right. Terms can be used once, more than once, or not at all.

Photosynthetic protists are often held in check by low concentrations of nitrogen, phosphorus, or iron. So, a drop in nutrient availability will cause a(n) decrease of abundance of photosynthetic protists, which will result in a(n) decrease of the abundance of consumers.

Why has the kingdom Protista been abandoned?

The second and third answers are correct. 1. The kingdom Protista is polyphyletic. 2. Some protists are multicellular. Recognizing that the kingdom Protista as originally defined was polyphyletic and that some protists are more closely related to other eukaryotes than to each other, scientists have abandoned the kingdom Protista and reorganized the entire domain Eukarya.

What evolutionary changes could occur if malaria control were attempted using such a Wolbachia strain versus using insecticides to kill mosquitoes? Match the terms in the left column to the appropriate blanks in the sentences on the right. Not all terms will be used.

The two approaches are different in the evolutionary changes they may bring. A strain of Wolbachia that confers resistance to infection by Plasmodium and does not harm mosquitoes would spread rapidly through the mosquito population. In this case, natural selection would favor any Plasmodium individuals that could overcome the resistance to infection. If insecticides were used, mosquitoes that are resistant to them would be favored the same way. Therefore, the use of Wolbachia could cause evolution in Plasmodium populations, while the use of insecticides could cause evolution in mosquito populations. The bacterium Wolbachia is a symbiont that lives in mosquito cells and spreads rapidly through mosquito populations. Wolbachia can make mosquitoes resistant to infection by Plasmodium; researchers are seeking a strain that confers resistance and does not harm mosquitoes.

How can the response of diatom populations to a drop in nutrient availability affect aspects of the physical environment (such as carbon dioxide concentrations)? Match the words in the left column to the appropriate blanks in the sentences on the right. Not all terms will be used.

Typically, diatoms are eaten by consumers, but during a bloom, many escape this fate. Uneaten diatoms die and their bodies sink to the ocean floor. As a result, the carbon in their bodies remains as organic compounds, rather than being released as CO2 as the decomposers respire.

Which group is considered to be the closest living relative of animals?

choanoflagellates In addition to DNA evidence uniting choanoflagellates with animals, choanoflagellate cells are morphologically similar to collar cells (choanocytes) of sponges.

A sign on the beach reads, "Beach Closed. Red Tide." The organisms interfering with use of this beach are probably __________.

dinoflagellates Dinoflagellate blooms, episodes of explosive population growth, cause red tides in coastal waters.

Which of the following are two groups that are adapted to anaerobic conditions and contain reduced mitochondria that lack DNA?

diplomonads and parabasalids Diplomonads and parabasalids are known for their reduced mitochondria.