Question 1 (1997)

Standards

Photosynthesis and cellular respiration recycle oxygen in ecosystems. Respond to TWO (and only two) of the following:

a. Explain how the metabolic processes of cellular respiration and photosynthesis recycle

oxygen.

b. Discuss the structural adaptations that function in oxygen exchange between each of the

following organisms and its environment: a plant; an insect; a fish.

c. Trace a molecule of O2 from the environment to a muscle cell in a vertebrate of your choice.

General Comments:

1. We will grade the FIRST two parts that the student discusses or starts to discuss.

2. A student can earn a maximum of 6 points on each of the two parts.

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a. Explain how the metabolic processes of cellular respiration and photosynthesis recycle oxygen. MAX. 6 Points

Cellular respiration

1 pt. Oxygen is a reactant OR is used in cellular respiration OR the correct equation

1 pt. Oxygen is used in Electron Transport System (ETS)

1 pt. Oxygen is the final electron (H) acceptor (oxygen is reduced)

1 pt. Water is formed (a byproduct)

1 pt. Electronegativity (redox potential) of oxygen enables it to be an electron (H) acceptor (have greater affinity for oxygen)

Photosynthesis

1 pt. Oxygen is a product (or the correct equation)

1 pt. Oxygen is formed (released) in light reactions (any aspect of the light reactions)

1 pt. Water donates electrons (H) (water is oxidized)

1 pt. Water is split to form oxygen, oxygen is derived from water (not carbon dioxide)

1 pt. Photorespiration; relevant rubisco discussion

Cycle

1 pt. Air (atmosphere) and/or water are reservoirs for oxygen (in context)

1 pt. Energy for splitting of water is from the sun

1 pt. Plants carry out both photosynthesis and cellular respiration

1 pt. Oxygen released by plants can be (is) recycled through animals/ plants/other (aerobic) organisms

b. Discuss the structural adaptations that function in oxygen exchange between each of the following organisms and its environment: a plant; an insect; a fish. MAX. 6 Points

The adaptations listed below do not constitute an exhaustive list of possible adaptations.

Points are awarded in the following manner:

Two points maximum for each kind of organism

1 point for the adaptation plus 1 point for a discussion of that adaptation

1 point/ organism for one or more adaptations with no discussion

1 point for each discussion (even if a specific adaptation is not named)

An acceptable discussion point was awarded for an explanation of the adaptation as it related to oxygen exchange. Many of the discussion points were associated with the items listed in the 'overview' points list.

Possible overview points (1 maximum) - These concepts are frequently used discussions or explanations of the adaptations.

Increase in surface area - for gas exchange

Thin surface for exchange

Balance moist surface with prevention of dehydration

Fick's Law of Diffusion (establishment of an oxygen concentration gradient)

Oxygen must be dissolved to diffuse across a membrane

Plant adaptations (2 Points Max.)

Stomates

Guard cells

Roots

Lenticels

Spongy Mesophyll or Spongy parenchyma

Leaves

Knees (cypress)

Insect adaptations (2 Points Max.)

Spiracles

Tracheae (branching tubes)

Respiratory pigments

Abdominal muscles

External gills (thoracic and abdominal)

Bubble capture

Liquid medium

Rectal gills

Fish adaptations (2 Points Max.)

Gills/gill filaments/

lamellae

Counter-current flow

Respiratory pigments

Closed circulatory system

Operculum

Lungs

Vascularization (capillaries)