Problem 4 - Campbell Biology

Question

Which of the following statements is a correct distinction between autotrophs and heterotrophs? (A) Autotrophs, but not heterotrophs, can nourish themselves beginning with CO2 and other nutrients that are inorganic. (B) Only heterotrophs require chemical compounds from the environment. (C) Cellular respiration is unique to heterotrophs. (D) Only heterotrophs have mitochondria.

Step-by-Step Solution

Answer

Option A is correct.

Step 1: Understand the key terms

Autotrophs are organisms that produce their own food from inorganic substances. Heterotrophs obtain their energy by consuming organic substances.

Step 2: Evaluate Option A

Autotrophs can nourish themselves beginning with CO2 and other inorganic nutrients. This is correct because plants, for example, use photosynthesis to convert CO2 and water into glucose.

Step 3: Evaluate Option B

Heterotrophs require organic chemical compounds from their environment, but autotrophs also need chemical compounds like water. This statement is incorrect.

Step 4: Evaluate Option C

Cellular respiration occurs in both autotrophs and heterotrophs. This statement is incorrect because plants also perform cellular respiration.

Step 5: Evaluate Option D

Both autotrophs (e.g., plant cells) and heterotrophs (e.g., animal cells) have mitochondria. This statement is incorrect.

Step 6: Select the correct option

From the evaluations, only Option A is a correct distinction between autotrophs and heterotrophs.

Key Concepts

autotrophs

Autotrophs are fascinating organisms that have the unique ability to produce their own food from inorganic substances.
Think of plants, algae, and some bacteria. They harness the power of sunlight through a process known as photosynthesis to convert carbon dioxide (CO2) and water (H2O) into glucose and oxygen (O2).
In other words, these organisms are self-sufficient in terms of nourishment.

Autotrophs are crucial for our planet because they form the base of the food chain. Without them, life on Earth would struggle to survive due to the lack of food and oxygen.
Understanding how they function can offer insight into various biological and ecological processes.

heterotrophs

Heterotrophs, on the other hand, cannot produce their own food.
Instead, they rely on consuming other organic substances for their energy and nutritional needs. This group includes animals, fungi, and many microorganisms.

Heterotrophs have various ways of obtaining food:

• Herbivores eat plants.
• Carnivores consume other animals.
• Omnivores take in both plants and animals.
• Decomposers break down dead organic matter.

Their dependence on organic matter makes them integral to the recycling of nutrients in an ecosystem as they break down complex organic compounds into simpler forms that can be reused by autotrophs.

cellular respiration

Cellular respiration is a fundamental process that occurs in both autotrophs and heterotrophs.
This process allows cells to generate energy from glucose, which is necessary for various cellular functions.
The general equation for cellular respiration is:



This enzymatic reaction involves multiple stages:

• Glycolysis
• Citric Acid Cycle (Krebs Cycle)
• Electron Transport Chain (ETC)

Cellular respiration mainly takes place in the mitochondria, often referred to as the powerhouse of the cell.
It's essential to note that this process is common to both autotrophs and heterotrophs, so the statement that cellular respiration is unique to heterotrophs is incorrect.

photosynthesis

Photosynthesis is a process used by autotrophs to convert light energy into chemical energy stored in glucose.
This process is crucial for producing the oxygen we breathe. The overall equation for photosynthesis is:

Photosynthesis occurs in two main stages: the light-dependent reactions and the Calvin cycle (light-independent reactions).

• Light-dependent reactions take place in the thylakoid membranes and produce ATP and NADPH.
• The Calvin cycle occurs in the stroma of the chloroplasts and synthesizes glucose.

Understanding photosynthesis helps us appreciate how energy flows through ecosystems and the vital role of autotrophs in maintaining life on Earth.