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Biological diversity

Ten questions of mixed difficulty, covering Biological diversity. Print it, or work through it on screen — the answer key starts on its own page.

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Biological diversity

Science 9 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. A human body cell has 46 chromosomes. A sperm cell, made by meiosis, has

    1. a) 92 chromosomes
    2. b) 1 chromosome, either an X or a Y
    3. c) 23 chromosomes
    4. d) 46 chromosomes

  2. A species' niche is

    1. a) its role in the ecosystem: what it eats, what eats it, how it lives
    2. b) the number of its members living in one area at one time
    3. c) the physical place where it lives, such as a pond, marsh or forest
    4. d) the other species it competes against for food and space

  3. Some organisms reproduce asexually while conditions are good, then switch to sexual reproduction when conditions get worse. The best explanation is that sexual reproduction

    1. a) produces many more offspring, in less time, than asexual reproduction does
    2. b) produces varied offspring, so some are likely to suit the new conditions
    3. c) needs no partner, so it is easier when food and space run short
    4. d) produces offspring identical to both parents, so they are protected

  4. Scientists move a gene from a bacterium into canola so the canola survives a weed-killer. How does this differ from selective breeding?

    1. a) Humans choose which plants reproduce, unlike in nature
    2. b) A gene is moved directly, even between unrelated species
    3. c) It takes many more generations to produce the same result
    4. d) Only plants of a single variety can be used in it

  5. In pea plants, purple flower colour (P) is dominant over white (p). A plant that inherited one P and one p has

    1. a) white flowers
    2. b) some purple and some white flowers
    3. c) pale purple flowers, a blend of both
    4. d) purple flowers

  6. Two warbler species eat insects in the same spruce trees. One feeds mostly at the tips of the highest branches; the other feeds mostly near the trunk, lower down. This most likely

    1. a) means one species will soon drive the other to extinction
    2. b) reduces competition, so both species can live in the same trees
    3. c) proves that the two species eat completely different foods
    4. d) shows the two birds are really one species with some variation

  7. A plantation grows only one banana variety, and every plant is a clone. A new fungus arrives that this variety cannot resist. The biggest danger is that

    1. a) the whole crop could be lost, since no plant has genes to resist it
    2. b) the fungus will cause mutations that make the plants resistant
    3. c) the bananas will quickly breed resistance among themselves
    4. d) only the oldest plants will die, since the young ones are stronger

  8. A bacterium copies its DNA and splits into two identical cells. This type of reproduction is

    1. a) spore formation
    2. b) binary fission
    3. c) sexual reproduction
    4. d) budding

  9. Which of these characteristics is heritable, meaning it is passed from parents to offspring through genes?

    1. a) A suntan from a summer outdoors
    2. b) Strong legs from training for track
    3. c) Natural eye colour
    4. d) A scar from a skateboarding fall

  10. Swift foxes once vanished completely from the Canadian prairies, although the species still survived in the United States. In Canada, the swift fox had become

    1. a) extinct
    2. b) extirpated
    3. c) invasive
    4. d) endangered

Answer key · Biological diversity

Science 9 · maddyhelps.com

  1. c) 23 chromosomes — Meiosis halves the number, so when a sperm (23) joins an egg (23) the offspring has 46 again. Keeping all 46 is what mitosis does, and the X or Y is just one of the sperm's 23.
  2. a) its role in the ecosystem: what it eats, what eats it, how it lives — A niche is a species' whole way of life: its food, its predators, and when and where it is active. The physical place is its habitat, and mixing up niche and habitat is the usual mistake.
  3. b) produces varied offspring, so some are likely to suit the new conditions — Mixing genes from two parents gives variety, and in a changing environment variety raises the odds that some offspring survive. Asexual reproduction is usually the faster way to multiply, which is exactly why it is used while conditions are good.
  4. b) A gene is moved directly, even between unrelated species — Genetic engineering changes the DNA directly and can take a gene from any organism. Selective breeding only chooses which parents mate, so it works with the variation a species already has and takes many generations.
  5. d) purple flowers — A dominant trait shows whenever at least one copy is present, so Pp looks purple. The white trait is still carried and can appear in the next generation, but traits do not blend, which is the mistake behind the pale purple answer.
  6. b) reduces competition, so both species can live in the same trees — Feeding in different parts of the tree splits the food supply, so the two species compete less and both survive. They may eat the same kinds of insects; it is where they feed that differs, and that is part of each one's niche.
  7. a) the whole crop could be lost, since no plant has genes to resist it — Clones share identical genes, so a disease that kills one can kill them all. Variation is a population's insurance, which is why seed banks store many varieties of each crop and not just today's best one.
  8. b) binary fission — Binary fission means splitting in two, and both new cells are identical to the parent. Budding is different: a small outgrowth forms on the parent, as in yeast, and breaks off later.
  9. c) Natural eye colour — Eye colour is set by genes inherited from both parents. The other three were acquired during one person's life, so they are not in the DNA and cannot be passed on: a parent's track training does not give a child strong legs.
  10. b) extirpated — Extirpated means gone from one region while the species survives somewhere else. Extinct means gone everywhere for good, and because swift foxes survived in the United States, they could later be returned to the Canadian prairies.