Question

biology scrimmage 1
carbon! where does it come from? where does it go?
on earth, carbon compounds are found in the oceans, atmosphere, and living organisms, as well as stored in rocks and sediments. earth and its atmosphere can be considered a closed system. the amount of carbon in different locations within earths systems is always changing.
sea otters help maintain the carbon balance in their ecosystem. otters eat sea urchins. eating sea urchins is important, as sea urchins are herbivores that can destroy a kelp forest. kelp are large seaweed algae that grow much faster than most plants. when kelp die, they sink into the deep ocean. the low oxygen conditions of the sea floor cause decomposition to be slow or incomplete.
scientists calculated the carbon pool (how much carbon kelp stores) with and without sea otters, as shown in the model below.

1. which claim about the kelp carbon pool is best supported by evidence from the information and the model above?

(1) the carbon storage is higher with the otters present because the sea otters eat the sea urchins.
(2) the carbon storage is higher with the sea urchins present because they control the kelp population.
(3) the carbon storage is lower with the otters present because the sea otters eat the kelp.
(4) the carbon storage is lower with the sea urchins present because they carry out autotrophic nutrition.

1. which statement uses the model to describe how kelp contributes to a reduction of carbon entering the atmosphere?

(1) kelp produces carbon as it grows within the hydrosphere.
(2) some of the carbon stored in the dead kelp is trapped in the geosphere of the sea floor.
(3) kelp produces carbon as it sinks into the hydrosphere.
(4) some of the carbon stored in kelp is added to the geosphere through cell respiration.

1. which model identifies the process that converts light energy into chemical energy inside the kelp?

Explanation:

Question 1

To solve this, we analyze each option:

• Option (1): The model shows kelp carbon pool is higher with otters (since otters eat sea urchins, which would otherwise destroy kelp). So sea otters eating sea urchins allows kelp to grow, increasing carbon storage. This matches.
• Option (2): Sea urchins destroy kelp, so their presence would lower kelp carbon storage, not increase. Eliminate.
• Option (3): Sea otters eat sea urchins, not kelp. Eliminate.
• Option (4): Sea urchins are herbivores (eat kelp), not autotrophs (autotrophs make their own food, like kelp). Eliminate.

Analyze each option for how kelp reduces carbon in atmosphere:

• Option (1): Kelp (autotroph) takes in carbon (CO₂) during photosynthesis, doesn't produce carbon as it grows. Eliminate.
• Option (2): When kelp dies, it sinks to sea floor (geosphere). Decomposition is slow there, so carbon is trapped in geosphere (sea floor), reducing carbon in atmosphere (since it's stored instead of released). This makes sense.
• Option (3): Kelp sinks after dying, not as it sinks into hydrosphere. Also, kelp takes in CO₂, doesn't produce carbon. Eliminate.
• Option (4): Cell respiration releases CO₂ (adds to atmosphere), which would increase carbon in atmosphere, not reduce. Eliminate.

The process that converts light energy to chemical energy in kelp is photosynthesis. Photosynthesis uses light energy to convert CO₂ and H₂O into glucose (chemical energy) and O₂.

• Option (1): Shows CO₂ + H₂O → glucose + O₂, but no light input (photosynthesis needs light). Eliminate.
• Option (2): Shows glucose + O₂ → CO₂ + H₂O (respiration), which releases energy, not stores. Eliminate.
• Option (3): Shows CO₂ + H₂O → glucose + O₂ with light (sun symbol), which is photosynthesis (converts light to chemical energy in glucose). Correct.
• Option (4): Shows glucose + O₂ → CO₂ + H₂O (respiration) with oxygen input, not light. Eliminate.

Answer:

(1) The carbon storage is higher with the otters present because the sea otters eat the sea urchins.

Question 2