Question

natural selection 1.4 snap shot assessment
snails eaten vs. snail shell color
references:
prolineserver. (2007, june 1). file:snail anim.gif. wikimedia commons.
https://commons.wikimedia.org/wiki/file:snail_anim.gif
(used under cc by - sa 3.0)
sanches, d. (2008). gavião - caramujeiro (rostrhamus sociabilis) photograph. wikimedia comm
kimedia.org/wiki/file:flickr_-_dario_sanches_-_gavi%c3%83o - caramujeiro_(rostrhamus_
(used under cc by - sa 2.0)
multiple choice

1. which statement about natural selection is true?

a. helpful traits always become more common in a population over time.
b. only animals with helpful traits will be able to survive and reproduce.
c. all animals have an equal chance of reproducing over time.
d. helpful traits can become more common in a population over time.
e. the largest animals in a species always have an advantage in surviving.
multiple choice

1. based on figure 4, which of these statements correctly describes the likely

populations?
a. the next generation of snails will have no light - colored shells.
b. over time the population of dark - colored snails will decrease.
c. the snail kites will not affect the next generation of snails
d. over time the population of light - colored snails will decrease.

Explanation:

Question 1

• Option A: "Always" is incorrect as other factors can affect trait prevalence.
• Option B: Animals without helpful traits can still survive/reproduce (just less likely), so "only" is wrong.
• Option C: Natural selection means unequal reproductive chances based on traits.
• Option D: Helpful traits (increasing survival/reproduction) can become more common over time (correct, as it's a probability, not a certainty like A).
• Option E: Size isn’t always an advantage; survival depends on context (e.g., energy needs, predation).

From the bar graph: Darkest snails eaten ≈ 0, medium ≈ 5, lightest ≈ 35. So light - colored snails are eaten more, dark - colored less.

• Option A: Light - colored snails are eaten more, but some may survive to reproduce, so next gen won’t have “no” light - colored shells.
• Option B: Dark - colored snails are eaten least, so they survive/reproduce more. Over time, their population (or relative prevalence) will increase? Wait, no—wait, the graph shows “Snails Eaten” by shell color. Darkest snails are eaten the least, so they have higher survival. So over time, dark - colored snails (with higher survival) will reproduce more, so the population of dark - colored snails will increase, and light - colored (eaten more) will decrease? Wait, no—the question is about the likely change in populations. Wait, the options:
• B: “Over time the population of dark - colored snails will decrease.” No, dark - colored are eaten least, so they survive more, so their population should increase. Wait, maybe I misread. Wait the graph: x - axis is Snail Shell Color (Darkest, [middle], Lightest). Y - axis: Snails Eaten. Darkest: ~0, middle: ~5, Lightest: ~35. So predators eat more light - colored snails. So light - colored snails have lower survival, so their population will decrease over time. Dark - colored snails have higher survival, so their population will increase over time.
• Option B: “Over time the population of dark - colored snails will decrease.” No, that's wrong. Wait option D: “Over time the population of light - colored snails will decrease.” That matches (since they are eaten more, so fewer survive to reproduce, population decreases). Wait but let's re - check:
• A: Next gen no light - colored: too extreme (some light - colored may survive).
• B: Dark - colored population decrease: no, they are eaten least, so increase.
• C: Snail kites (predators) affect next gen (since they eat snails, reducing those eaten, so affecting reproduction). So C is wrong.
• D: Light - colored snails are eaten most, so their survival/reproduction is lower. Over time, their population will decrease (correct). Wait, but earlier I thought dark - colored would increase, but the option B says “dark - colored population will decrease” (wrong), D says “light - colored population will decrease” (correct).

Answer:

D. Helpful traits can become more common in a population over time.

Question 2