CSEC Biology Paper 1 May/June 2026 - Free CXC Past Paper with Answers

Which of the following features is used to classify a group of organisms as Class Insecta?

Which of the following sampling methods is MOST suitable for estimating the density of mushrooms in a garden?

Mark/Release/Recapture

Which of the following correctly defines a niche and a habitat?

The role that an organism plays in the habitat in which it lives / The place where an organism lives

The place where an organism lives / The role that an organism plays in the habitat in which it lives

A community of living organisms that share the environment / The abiotic and biotic factors of the ecosystem in which an organism lives

The biotic factors of the ecosystem where an organism lives / The abiotic factors of the ecosystem where an organism lives

Trophic level 1 is represented by

small fish and crustaceans

Which of the following organisms are MOST important in biodegradation?

Which of the following relationships may present harm to one of the organisms involved?

I. Commensalism II. Parasitism III. Predation

Approximately $10%$ of the energy stored in food is available to the next organism in a food chain because

most of the energy is lost as heat during the process of respiration

most of the energy is lost during the process of excretion

there are fewer consumers than producers in a food chain

many consumers compete for the same food source

Which of the following processes convert organic matter to inorganic forms?

Human activities would have the LEAST immediate impact on

the formation of fossil fuels

Replanting trees on a bare hillside is an example of

restoration and preservation

reafforestation and restoration

conservation and afforestation

preservation and conservation

Phase 4 of the graph of population growth is MOST likely due to

competition from invasive species

adequate food and space

a high natural birth rate

When compared to a cheek cell, a muscle cell contains more

Which of the following comparisons between the cell wall and cell membrane is INCORRECT?

Found in both plant and animal cells / Found in animal cells only

Freely permeable / Differentially permeable

Contains cellulose / Does not contain cellulose

Found in plant cells only / Found in both plant and animal cells

The MAJOR feature that is responsible for the rigid structure of the xylem vessel is the

gap where two cells meet

What can be done to cause the level of the solution in the petri dish to rise after 20 minutes?

Add 5 g of salt to the distilled water in the potato only.

Add 5 g of salt to the distilled water in the petri dish only.

Add 5 g of salt to the distilled water in both the petri dish and the potato.

Add 0 g of salt to the distilled water in both the petri dish and the potato.

Autotrophic organisms derive their nutrition from

I. water II. simple inorganic substances III. complex organic substances

Which of the following features would NOT enhance a leaf's ability to absorb solar energy?

Presence of a vascular bundle

Numerous chloroplasts in the palisade cells

Which of the following statements BEST accounts for the shape of the graph?

As photosynthesis rates increase, there is a decrease in carbon dioxide levels.

As light intensity increases, there is an increase in photosynthesis until there is no further increase in the rate due to some other limiting factor.

As light intensity increases, the rate of photosynthesis also increases until there is an increase in photosynthesis until the rate of photosynthesis also increases until denaturation of the enzymes occurs.

As carbon dioxide levels gradually increase, there is a similar increase in the rate of photosynthesis until a plateau phase exists, where no further increase in carbon dioxide results in any further increase in photosynthesis.

The samples X, Y, and Z MOST likely contain

non-reducing sugar / starch / protein

protein / reducing sugar / starch

starch / protein / reducing sugar

protein / starch / non-reducing sugar

Which region of the tooth contains a large number of blood vessels and nerves?

A 50-year-old male is advised by his doctor to reduce the amount of salt he consumes in his diet. If he ignores his doctor's advice, he has a high chance of developing

Which of the labelled parts represents the rib?

The energy released from the process above is

stored in a high energy bond in ADP

stored in a high energy bond in CDP

Which of the following conditions is an effect of the carbon monoxide found in cigarette smoke?

Increased heart rate

Increased beating of cilia

Reduced oxygen transport in the blood

Increased mucus production in the cells lining the respiratory passage

An amoeba obtains all the oxygen it needs by diffusion via its cell membrane, while a human needs to have special respiratory surfaces for this purpose. The BEST explanation for this difference is that

the amoeba does not require much oxygen

oxygen cannot pass through the skin of a human

a human requires a larger volume of oxygen

a human's surface area to volume ratio is too small for diffusion to be effective

Which of the following features can be found in red blood cells?

I. Nucleus II. Bi-concave shape III. Thin membrane

In which of the following plant tissues are tracheids found?

I. Xylem II. Phloem III. Epidermis

Artificial immunity can BEST be described as immunity

acquired from the body's natural defense against disease

produced by deliberate exposure to a pathogen

that has been passed on from mother to child in the uterus

that has been passed on to a child from a mother's colostrum

The activities, I, II, III and IV, listed below are involved in the clotting of blood.

I. Fibrinogen is converted to fibrin. II. Blood cells are trapped. III. Platelets are activated. IV. Blood vessels are damaged.

Which of the following correctly lists the sequence of activities?

In the transport of solutes in the phloem, the source is defined as any area of the plant where

water is loaded into the phloem

sucrose is loaded into the phloem

water is taken out of the phloem

sucrose is taken out of the phloem

Which part of the plant contains the MOST starch?

Which of the following substances is removed during egestion?

Which of the following correctly describes movement in plants?

Irreversible, whole or part movement

Reversible, whole or part movement

Irreversible, growth or part movement

Reversible, growth or part movement

Locomotion is an evolutionary adaptation performed by animals. What advantages does this mechanism have over the type of movement that occurs in plants?

I. The ability to move to favourable conditions II. The increased chance of predator attacks III. The ability to find food

Which of the following options BEST describes the terms 'stimulus' and 'response'?

A deliberate provocation of an organism / The movement of an organism

An organism's exposure to sunlight / The growth of an organism away from light

A wave of excitement in an organism / Locomotion of an organism

A detectable change in an organism's environment / An organism's reaction to a change in its environment

The numbered structures are

sensory neurone / motor neurone / relay neurone

motor neurone / sensory neurone / relay neurone

sensory neurone / relay neurone / motor neurone

motor neurone / relay neurone / sensory neurone

Which labelled structure relays the impulse to an effector?

The function of the choroid layer in the eye is to

focus most light rays

prevent internal reflection

maintain the shape of the eyeball

control the amount of light entering the eye

Which structure is NOT involved in temperature regulation?

The statements below describe the processes taking place within a seed during germination.

I. The embryo uses food to develop the radicle and plumule. II. Enzymes break down proteins into amino acids. III. Soluble products move into the embryo.

Which of the following sequences of events occurs during the germination of the seed?

I $\rightarrow$ II $\rightarrow$ III

I $\rightarrow$ III $\rightarrow$ II

II $\rightarrow$ I $\rightarrow$ III

II $\rightarrow$ III $\rightarrow$ I

Which of the following structures is common to both cells?

The production of new organisms from one parent only is known as

asexual reproduction

Which of the following sequences is the correct order of activities?

I $\rightarrow$ II $\rightarrow$ III $\rightarrow$ IV

II $\rightarrow$ I $\rightarrow$ III $\rightarrow$ IV

IV $\rightarrow$ III $\rightarrow$ II $\rightarrow$ I

IV $\rightarrow$ I $\rightarrow$ II $\rightarrow$ III

Which of the following forms of birth control is MOST likely 100% effective?

Which of the following statements is true concerning the flowers?

I is pollinated by a hummingbird; II is pollinated by the wind.

Both are pollinated by hummingbirds.

Petals are absent from both I and II.

Both are wind pollinated.

Which of the following shows the correct sequence for seed formation after fertilization?

Ovule $\rightarrow$ zygote $\rightarrow$ embryo $\rightarrow$ seed

Ovule $\rightarrow$ embryo $\rightarrow$ seed $\rightarrow$ zygote

Embryo $\rightarrow$ ovule $\rightarrow$ zygote $\rightarrow$ seed

Embryo $\rightarrow$ zygote $\rightarrow$ ovule $\rightarrow$ seed

A vector is defined as an organism that

lives on other organisms

transmits disease-carrying organisms

At which stage is this vector easily controlled by the use of aerosol insecticides?

A 60-year-old man has been diagnosed with hypertension as well as diabetes. Which of the following treatments would be MOST effective for the diseases?

Exercising and lowering the intake of salt and refined carbohydrates

Spending more time watching television to relax

Starting a rigorous exercise programme

Taking insulin injections

Which of the following statements BEST describes a chromosome?

Two forms of the same gene

Structure made up of DNA wrapped around histones

Nucleic acid that contains all genetic information

Part of the DNA which carries genetic information to produce a protein

The correct order of the stages is

On a certain Caribbean island where sugar cane is grown, a fungus is accidentally introduced into the island and destroys the entire sugar cane crop. Which of the following BEST explains why the entire crop was destroyed by the fungus?

The plants were old and therefore more susceptible to the fungus.

The plants were not of a hardy enough variety to withstand the fungus.

The plants were planted too close together so the fungus spread easily.

There was no genetic variation among the plants so none could survive the attack.

Which of the following statements about meiosis is NOT true?

It allows for genetic variation.

It results in the production of gametes.

It doubles the number of chromosomes in gametes.

It causes haploid cells to form from diploid cells.

In pea plants, purple flowers are dominant over white flowers. What percentage of the offspring are likely to have white flowers in the following crosses?

Albinism is caused by a recessive allele. Two normal parents produce an albino child. This is because

both parents were homozygous recessive

both parents were heterozygous for the gene

one parent was homozygous dominant for the trait and the other heterozygous

one parent was homozygous dominant for the trait and the other homozygous recessive

Two goats, heterozygous for fast growth rate, are crossed. What percentage of the entire F1 population would be expected to possess homozygous alleles?

Variation in populations is due to I. mutation II. crossing over III. asexual reproduction

A species consists of members that

occupy the same habitat

reproduce by asexual means

interbreed under natural conditions

interbreed to produce infertile offspring

Which of the following descriptions is true of natural and artificial selection?

Produces great biological diversity / Produces very different organisms from natural populations

Involves genetic modification / Largely controlled by the environment

Occurs in domestic populations / Occurs in natural populations

Is a faster process / Is a slower process

In which of the stages above can insulin be produced by the bacterium?

CSEC Biology Paper 1 May/June 2026 - Free CXC Past Paper with Answers

CSEC Biology Paper 1 May/June 2026 Questions