Q: A population of fish in a lake has a birth rate of 0.2 per year and a death rate of 0.1 per year. If the current population size is 500, what is the expected change in population size after one year, assuming no immigration or emigration?

$$\Delta N = (b - d) \times N = (0.2 - 0.1) \times 500 = 50$$

Question 1

Which of the following best explains why Gram-negative bacteria are generally more resistant to antibiotics than Gram-positive bacteria?

Accepted Answer

Gram-negative bacteria possess an outer membrane with lipopolysaccharides that restricts antibiotic penetration.

Question 2

A scientist discovers a unicellular organism with a nucleus, mitochondria, and flagella. It is capable of photosynthesis and sexual reproduction. To which group does this organism most likely belong?

Accepted Answer

Protists

Question 3

Which structure in fungi is primarily responsible for nutrient absorption and why?

Accepted Answer

Mycelium, because its extensive network of hyphae increases surface area for absorption.

Question 4

During the Cambrian explosion, which factor most directly contributed to the rapid diversification of animal body plans?

Accepted Answer

Increase in atmospheric oxygen

Question 5

Which of the following is a key difference between diploblastic and triploblastic animals?

Accepted Answer

Diploblastic animals lack a mesoderm, while triploblastic animals possess a mesoderm.

Question 6

A population of fish in a lake has a birth rate of 0.2 per year and a death rate of 0.1 per year. If the current population size is 500, what is the expected change in population size after one year, assuming no immigration or emigration?

Accepted Answer

$$\Delta N = (b - d) 	imes N = (0.2 - 0.1) 	imes 500 = 50$$

Question 7

Which of the following best describes the role of xylem in vascular plants?

Accepted Answer

Transports water and minerals from roots to shoots

Question 8

In the ABC model of flower development, a mutation that inactivates B genes would result in which floral organs?

Accepted Answer

Sepals and carpels only

Question 9

Which process in the nitrogen cycle is performed by bacteria such as Rhizobium and is essential for making nitrogen available to plants?

Accepted Answer

Nitrogen fixation

Question 10

A patient is exposed to a pathogen and later shows a rapid, strong immune response upon re-exposure. Which type of immune cell is primarily responsible for this response?

Accepted Answer

Memory B and T cells

Question 11

Which of the following best explains why marine fish must actively excrete salts and drink seawater?

Accepted Answer

They are hypoosmotic to their environment and lose water by osmosis.

Question 12

Which hormone is released from the posterior pituitary and increases water reabsorption in the kidney?

Accepted Answer

Antidiuretic hormone (ADH)

Question 13

Which of the following is a major advantage of sexual reproduction over asexual reproduction in animals?

Accepted Answer

Sexual reproduction allows for greater genetic variation and adaptability.

Question 14

During an action potential, which event is responsible for the rapid depolarization phase?

Accepted Answer

Opening of voltage-gated Na$$^+$$ channels and influx of Na$$^+$$ ions

Question 15

Which part of the brain is primarily responsible for coordination and balance?

Accepted Answer

Cerebellum

Question 16

Which of the following best describes the function of mechanoreceptors in sensory systems?

Accepted Answer

Detect physical deformation such as pressure, vibration, and stretch

Question 17

In muscle contraction, what is the role of calcium ions (Ca$$^{2+}$$)?

Accepted Answer

Ca$$^{2+}$$ binds to troponin, causing tropomyosin to move and exposing myosin-binding sites on actin.

Question 18

Which of the following is a consequence of biomagnification in ecosystems?

Accepted Answer

Toxins such as DDT and mercury accumulate at higher trophic levels, increasing risk to top predators.

Question 19

Which equation correctly represents the logistic growth of a population?

Accepted Answer

$$\frac{dN}{dt} = rN \left( \frac{K-N}{K} \right)$$

Question 20

Which adaptation allows homeotherms to maintain a stable body temperature in cold environments?

Accepted Answer

Countercurrent heat exchange in extremities

General Biology Study Notes: Diversity of Life, Physiology, and Ecology

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