What is common between the muscle fibers of extensor of human back and those of flight muscles of the birds which remain in flight for long periods of time ?
a. They are thinner , red colored
b, they are thicker and light colored .
c. they have abundant mitochondria .
d. they have well developed sarcoplasmic reticulum
e. they show rate of contractions for longer periods
f, They show fast strenuous activity
g. They do not get fatigued early .
h. They get fatigued quickly .

Options

A. a,c,e,g ,are common
B. b,d,f,h are common
C. All features are common at different times
D. a,c,f,g are common

Answer

To solve the question regarding the common characteristics between the muscle fibers of the extensor of the human back and the flight muscles of birds, we can follow these steps:

### Step-by-Step Solution:

1. **Identify Muscle Types**:
- Understand that there are two main types of muscle fibers: red (slow-twitch) and white (fast-twitch) muscles.
- Red muscles are characterized by their endurance and ability to sustain prolonged activity.

2. **Characteristics of Red Muscles**:
- Red muscles, such as the extensor muscles in the human back and the flight muscles in birds, contain a high amount of myoglobin, which gives them a red color.
- They also have abundant mitochondria, which are essential for aerobic respiration and energy production over extended periods.

3. **Fatigue Resistance**:
- Red muscle fibers are known for their ability to resist fatigue. They can contract for longer periods without tiring, making them suitable for activities like maintaining posture in humans and sustained flight in birds.

4. **Comparison with White Muscles**:
- White muscles, in contrast, are less resistant to fatigue and are designed for quick bursts of activity. They have less myoglobin and fewer mitochondria.

5. **Analyze the Options**:
- **a. They are thinner, red colored**: True for red muscles.
- **b. They are thicker and light colored**: False; this describes white muscles.
- **c. They have abundant mitochondria**: True for red muscles.
- **d. They have well-developed sarcoplasmic reticulum**: False; this is more characteristic of white muscles.
- **e. They show rate of contractions for longer periods**: True for red muscles.
- **f. They show fast strenuous activity**: False; this describes white muscles.
- **g. They do not get fatigued early**: True for red muscles.
- **h. They get fatigued quickly**: False; this describes white muscles.

6. **Conclusion**:
- The common features between the muscle fibers of the extensor of the human back and the flight muscles of birds are:
- They are red colored (a).
- They have abundant mitochondria (c).
- They show rate of contractions for longer periods (e).
- They do not get fatigued early (g).
- Therefore, the correct options are **a, c, e, and g**.

### Final Answer:
The common characteristics are: **a, c, e, and g**.

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