Topic 4 Ecology: Ecosystems

Question 1

• Ecosystems have trophic levels that categorize plants and animals based on their main energy source.

Answer 1

Note

Question 2

• Autotrophs that convert the sun’s energy into chemical energy. Primary producers include plants, photosynthetic protists, cyanobacteria, and chemosynthetic bacteria. Their efficiency from sunlight is only about 1% of the energy available to them

Answer 2

1. Primary Producers

Question 3

• These are herbivores. They have long digestive tracts with greater surface area so there is more time for digestion. Symbiotic bacteria in the digestive tract breaks down the cellulose which the herbivore itself cannot digest. Primary consumers eat primary producers

Answer 3

2. Primary Consumers

Question 4

• These are primarily carnivores, and they eat primary consumers

Answer 4

3. Secondary Consumers

Question 5

• They are secondary carnivores, and they eat secondary consumers

Answer 5

4. Tertiary Consumers

Question 6

• Consumers that obtain energy by consuming detritus. Detritus is nonliving organic material. It can be the remains of dead organisms, but also can be feces, fallen leaves, or wood. Smallest detritivores are decomposers such as fungi and bacteria. Other detritivores include nematodes, earthworms, insects, scavengers (vultures, jackals, crab), and saprophytes

Answer 6

5. Detritivores

Question 7

• Show the relationships between trophic levels, or biomass.

Answer 7

Ecological Pyramids

Question 8

• Describes the proportion of energy represented at one trophic level that is transferred to the next. On average, an efficiency of about 10% is transferred to the next. 90% of the energy is lost to metabolism and to detritivores when they die. Energy/biomass/quantity is greatest at the primary producer level and lowest at the tertiary consumer level. Tertiary level is least stable and most sensitive to the population fluctuations from the lower levels. Because ecological efficiency is so low, domesticated animals used for work are herbivores at lower trophic levels. If carnivores were domesticated for work instead, the energy required to raise and sustain the animals would be greater than the animal’s value returned in food or work.
• Do not confuse trophic efficiency with production efficiency (percentage of energy stored in assimilated food that is not used for respiration or excreted as feces). Birds and mammals have low product efficiency because they use lots of energy to maintain a constantly high body temperature. Fish, which are ectothermic, have higher production efficiencies, and insects and microorganisms are higher still.

Answer 8

Ecological/trophic efficiency

Question 9

• Linear flow chart of who’s eaten by whom

Answer 9

Food Chain

Question 10

• Is an expanded, more complete version of a food chain showing major plants, animals that eat the plants, animals that eat the animals, detritivores, etc. The greater the number of pathways in a community food web, the more stable the community is.

Answer 10

Food Web