A LEVEL BIOLOGY A (SNAB): PAST PAPER 1
& GRADING GUIDE THE NATURAL
ENVIRONMENT AND SPECIES SURVIVAL
ALL ASSESSMENT & LEVEL-BY-LEVEL
MARK SCHEME PRACTICE EXAMINATION
2026 QUESTIONS WITH ANSWERS
GRADED A+
◍ population.
Answer: a group of individuals that can interbreed and are living in the same
place at the same time
◍ In mutualism, is the benefit always complete?.
Answer: No, the benefit only needs to outweigh the cost.
◍ Students use vinegar to dissolve away the shells of three eggs and use these
eggs as models of human red blood cells. The students observe the changes
in the eggs when they are placed in different solutions.— Which statement
best describes the role of the cell membrane in this model.
Answer: The cell membrane allows water to enter and leave the cell
◍ How should this animal be classified.
Answer: Platyhelminthes
◍ interspecific interaction examples.
Answer: competition, predation, herbivory, mutualism, parasitism, and
commensalism
◍ Consumers.
, Answer: An organism that obtains energy and nutrients by feeding on other
organisms or their remains.
◍ what effects do keystone species have on communities?.
Answer: these effects can be disproportionate because many other species
may depend directly or indirectly on the species
◍ primary consumer.
Answer: An organism that eats producers
◍ Telophase is a stage of a cellular process that begins after the chromosomes
have moved to opposite poles of the cell. During which cellular process does
telophase occur?.
Answer: Mitosis
◍ biomass/kcal between trophic levels.
Answer: You get 10% between trophic levels, so if one has 100, the next has
10, then 1
◍ biodiversity.
Answer: the variety of life in the world or in a particular habitat or
ecosystem.
◍ The order of biological organization from smallest to largest.
Answer: Organism, population, community, ecosystem
◍ How do an increase in the organic matter in soil and an increase in soil
depth affect the population of plants in an area?.
Answer: Larger plant become the dominant organism
◍ According to the logistic growth equation Nt = N1 + rN1 [(K - N1)/ K])....
Answer: the number of individuals added per unit time is zero when N
equals K.
◍ Imagine that you are managing a large ranch. You know from historical
accounts that wild sheep used to live there, but they have been driven out of
that area completely and are no longer present. After doing some research to
determine what might be an appropriately sized starting population that is
, far below carrying capacity, you reintroduce wild sheep to your land. You
then watch the population increase rapidly for three generations, and graph
the number of individuals (vertical axis) against the number of generations
that have occured (horizontal axis). The graph will appear as….
Answer: a ʺJ,ʺ increasing with each generation.
◍ As ecosystems move through the stages of succession, the populations of
organisms in them change. Which of the following describes the stage of
succession likely to have the most species diversity?.
Answer: A temperate forest that has never been cleared by logging
◍ Roads are often built through forests for industrial purposes or as la nd is
develo for residential and commercial needs. How would road construction
throug h a forest most likely affect the ecosystem?.
Answer: The natural succession of vegetation would change
◍ What student made observations of a community of organisms.
Answer: Student 2
◍ Which of these factors impacting population size is independent of the
density of a population?.
Answer: A hurricane wipes out over half of a population of fish
◍ Which cells in the phase mitosis.
Answer: Cell 2
◍ phylogenetic niche conservatism.
Answer: some aspect of the niches of closely related species is similar, and
so are evolutionarily conserved
◍ secondary consumer.
Answer: An organism that eats primary consumers
◍ People who have leukemia, a cancer that affects white blood cells, are often
given Cytarabine. This drug inhibits the synthesis of DN
A. Which phase of the cell cycle is most affected by Cytarabine?.
Answer: S phase
& GRADING GUIDE THE NATURAL
ENVIRONMENT AND SPECIES SURVIVAL
ALL ASSESSMENT & LEVEL-BY-LEVEL
MARK SCHEME PRACTICE EXAMINATION
2026 QUESTIONS WITH ANSWERS
GRADED A+
◍ population.
Answer: a group of individuals that can interbreed and are living in the same
place at the same time
◍ In mutualism, is the benefit always complete?.
Answer: No, the benefit only needs to outweigh the cost.
◍ Students use vinegar to dissolve away the shells of three eggs and use these
eggs as models of human red blood cells. The students observe the changes
in the eggs when they are placed in different solutions.— Which statement
best describes the role of the cell membrane in this model.
Answer: The cell membrane allows water to enter and leave the cell
◍ How should this animal be classified.
Answer: Platyhelminthes
◍ interspecific interaction examples.
Answer: competition, predation, herbivory, mutualism, parasitism, and
commensalism
◍ Consumers.
, Answer: An organism that obtains energy and nutrients by feeding on other
organisms or their remains.
◍ what effects do keystone species have on communities?.
Answer: these effects can be disproportionate because many other species
may depend directly or indirectly on the species
◍ primary consumer.
Answer: An organism that eats producers
◍ Telophase is a stage of a cellular process that begins after the chromosomes
have moved to opposite poles of the cell. During which cellular process does
telophase occur?.
Answer: Mitosis
◍ biomass/kcal between trophic levels.
Answer: You get 10% between trophic levels, so if one has 100, the next has
10, then 1
◍ biodiversity.
Answer: the variety of life in the world or in a particular habitat or
ecosystem.
◍ The order of biological organization from smallest to largest.
Answer: Organism, population, community, ecosystem
◍ How do an increase in the organic matter in soil and an increase in soil
depth affect the population of plants in an area?.
Answer: Larger plant become the dominant organism
◍ According to the logistic growth equation Nt = N1 + rN1 [(K - N1)/ K])....
Answer: the number of individuals added per unit time is zero when N
equals K.
◍ Imagine that you are managing a large ranch. You know from historical
accounts that wild sheep used to live there, but they have been driven out of
that area completely and are no longer present. After doing some research to
determine what might be an appropriately sized starting population that is
, far below carrying capacity, you reintroduce wild sheep to your land. You
then watch the population increase rapidly for three generations, and graph
the number of individuals (vertical axis) against the number of generations
that have occured (horizontal axis). The graph will appear as….
Answer: a ʺJ,ʺ increasing with each generation.
◍ As ecosystems move through the stages of succession, the populations of
organisms in them change. Which of the following describes the stage of
succession likely to have the most species diversity?.
Answer: A temperate forest that has never been cleared by logging
◍ Roads are often built through forests for industrial purposes or as la nd is
develo for residential and commercial needs. How would road construction
throug h a forest most likely affect the ecosystem?.
Answer: The natural succession of vegetation would change
◍ What student made observations of a community of organisms.
Answer: Student 2
◍ Which of these factors impacting population size is independent of the
density of a population?.
Answer: A hurricane wipes out over half of a population of fish
◍ Which cells in the phase mitosis.
Answer: Cell 2
◍ phylogenetic niche conservatism.
Answer: some aspect of the niches of closely related species is similar, and
so are evolutionarily conserved
◍ secondary consumer.
Answer: An organism that eats primary consumers
◍ People who have leukemia, a cancer that affects white blood cells, are often
given Cytarabine. This drug inhibits the synthesis of DN
A. Which phase of the cell cycle is most affected by Cytarabine?.
Answer: S phase
