1. In which of the following levels of classification are the members most similar?

A. Order
B. Genus
C. Species ✔

D. Phylum

Explanation:
Members of the same species share the greatest number of characteristics.

2. The diagram represents a

A. cell
B. filament ✔

C. colony
D. part of a living organism

Explanation:
Spirogyra consists of cylindrical cells joined end to end, forming a filament.

3. Pyrenoid is present in the structure labeled

A. IV
B. III
C. II ✔

D. I

Explanation:
The pyrenoid is found in the chloroplast of Spirogyra.

4. Spirogyra is regarded as a multicellular plant because

A. the cylindrical cells are linked end to end ✔

B. its cells are linked together by cytoplasmic strands
C. its cells are large
D. it is an algae containing a large vacuole

Explanation:
Many similar cells joined together indicate multicellularity.

5. Which of the following pairs of structures in living organisms do not perform similar functions?

A. Lungs and spiracles
B. Root hairs and mammalian hairs ✔

C. Feathers and scales
D. Contractile vacuole and kidneys

Explanation:
Root hairs absorb water, while mammalian hairs serve protection and insulation.

6. Which of the following sequences is the correct arrangement of tissues in a young dicotyledonous stem from the inside to the outside?

A. Pith, phloem, cambium, xylem, parenchyma, collenchyma and epidermis
B. Xylem, phloem, cambium, cortex, endodermis, collenchyma and epidermis
C. Pith, xylem, cambium, phloem, collenchyma, parenchyma and epidermis ✔

D. Phloem, xylem, cambium, cortex, endodermis, collenchyma and epidermis

Explanation:
This is the correct anatomical arrangement of tissues in a dicot stem.

7. An animal which possesses scales, nares, and a backbone is likely to be a

A. toad
B. lizard ✔

C. rat
D. bat

Explanation:
Lizards are reptiles with scales, nostrils, and a backbone.

8. The opening of the guard cells of the epidermis in plants is by the process of

A. osmosis ✔

B. diffusion
C. active transport
D. transpiration

Explanation:
Water enters guard cells by osmosis, causing them to open.

9. What happens to a plant if the shoot tip is cut off and replaced by an agar block containing auxin?

A. stop growing
B. grow rapidly
C. continue to grow normally ✔

D. die completely

Explanation:
Auxin promotes growth, so normal growth continues.

10. Anaerobic respiration results in the production of

A. more energy than aerobic respiration
B. no energy
C. an equal amount of energy to aerobic respiration
D. less energy than aerobic respiration ✔

Explanation:
Anaerobic respiration releases less energy due to incomplete glucose breakdown.

11. Which of the following is not a skeletal tissue?

A. Plasma ✔

B. Chitin
C. Cartilage
D. Bone

Explanation:
Plasma is the liquid part of blood, not a skeletal tissue.

12. Which of the following statements is not correct about the mammalian heart?

A. Oxygenated blood enters the left auricle from the pulmonary vein
B. The walls of the ventricle are thicker than those of the auricle
C. Blood passes from the right ventricle to the left auricle through the aorta ✔

D. The tricuspid valve prevents backflow into the right auricle

Explanation:
Blood flows from the right ventricle to the lungs, not to the left auricle.

13. Which of the following organs are used for gaseous exchange in a mature toad?

A. Gills, lungs, and eardrum
B. Lungs, mouth, and eardrum
C. Mouth, skin, and gills
D. Skin, lungs, and mouth ✔

Explanation:
Adult toads respire through lungs, skin, and buccal cavity.

14. Which of the following statements about the diaphragm of a mammal is not correct?

A. separates the thorax and the abdomen
B. is a thick layer of muscle
C. is made of epithelial cells ✔

D. is part of the respiratory apparatus

Explanation:
The diaphragm is made of muscle, not epithelial cells.

15. Which of the following structures is used for respiration in insects?

A. Lungs
B. Thorax
C. Cuticle
D. Spiracles ✔

Explanation:
Insects respire through spiracles connected to tracheae.

16. A substance present in the glomerular filtrate in the mammalian kidney is

A. glucose ✔

B. fibrinogen
C. albumen
D. blood platelets

Explanation:
Glucose is small enough to pass through the glomerulus.

17. In humans, excretion of hypertonic urine is associated with the

A. distal convoluted tubule
B. loop of Henle ✔

C. Bowman's capsule
D. proximal convoluted tubule

Explanation:
The loop of Henle concentrates urine by water reabsorption.

18. The maintenance of a stable internal environment within the body of a mammal is known as

A. osmosis
B. plasmolysis
C. homeostasis ✔

D. excretion

Explanation:
Homeostasis maintains constant internal conditions.

19. Which part of the nephron is associated with ultrafiltration?

A. Distal convoluted tubule
B. Proximal convoluted tubule
C. Collecting duct
D. Bowman's capsule ✔

Explanation:
Ultrafiltration occurs in the Bowman's capsule.

20. Which of the following conditions would result in a decrease in the production of antidiuretic hormone?

A. Abnormally high blood sugar level
B. Drinking large quantities of water ✔

C. Increase in osmotic pressure of blood
D. Period of strenuous exercise

Explanation:
Excess water intake reduces ADH secretion.

21. Which of the following structures is not essential in a wind-pollinated flower?

A. Anther
B. Ovary
C. Stigma
D. Petal ✔

Explanation:
Wind-pollinated flowers do not need petals.

22. Which part of the flower produces the structure labeled III?

A. Carpel
B. Pollen
C. Stigma
D. Anther ✔

Explanation:
The anther produces pollen grains.

23. The parts labeled III and IV respectively are called

A. pollen tube and style
B. pollen grain and pollen tube ✔

C. anther and filament
D. stigma and style

Explanation:
Label III is pollen grain, while IV is the pollen tube.

24. Which of the labeled parts would become a component of the seed after fertilization?

A. I
B. II ✔

C. IV
D. V

Explanation:
The ovule develops into the seed after fertilization.

25. The resolution of a microscope refers to its power to

A. increase an object's apparent size
B. distinguish clearly between two objects ✔

C. scan the surface of an object
D. focus on an object

Explanation:
Resolution is the ability to separate two close points.

26. The process by which plants manufacture food from carbon dioxide and water using energy from the sun is called

A. chemosynthesis
B. photosynthesis ✔

C. anabolism
D. catabolism

Explanation:
Photosynthesis uses sunlight to produce food.

27. Conduction of water and mineral salts through the xylem vessels is enhanced because the xylem cells are

A. thickened with lignin
B. long, narrow tubes placed end to end ✔

C. close to the endodermis
D. centrally placed in the roots

Explanation:
Their tubular structure allows easy flow of water.

28. Which of the following factors is likely to increase the rate of transpiration in plants?

A. Reduction in the number of stomata
B. Increase in humidity
C. Increase in leaf surface area to volume ratio ✔

D. Removal of leaves

Explanation:
Larger leaf surface area increases water loss.

29. The enzyme that catalyzes the conversion of glucose to glucose-6-phosphate at the beginning of glycolysis is

A. phosphofructokinase
B. glucose isomerase
C. hexokinase ✔

D. glucose-6-kinase

Explanation:
Hexokinase initiates glycolysis.

30. The correct arrangement of food classes of the same quantity in descending order of energy value is

A. Carbohydrates, fats and oils, water, protein
B. Fats and oils, carbohydrates, protein, water ✔

C. Water, fats and oils, carbohydrates, protein
D. Protein, fats and oils, water, carbohydrates

Explanation:
Fats yield the highest energy, water yields none.

31. Which of the following substances is not a complex carbohydrate?

A. Glycogen
B. Cellulose
C. Starch
D. Glucose ✔

Explanation:
Glucose is a simple sugar.

32. Which of the following associations is an example of epiphytism?

A. Lice in human hair
B. Mistletoe on citrus fruit
C. Egret on cow
D. Fern on palm tree ✔

Explanation:
Epiphytes grow on plants without harming them.

33. What is the likely food of the bird in I?

A. Worms ✔

B. Seed
C. Nectar
D. Fishes

Explanation:
The beak shape indicates worm feeding.

34. The food of the bird in II is

A. Worms
B. Seed ✔

C. Nectar
D. Fishes

Explanation:
Short, strong beaks are adapted for seed eating.

35. Ecology simply means the study of

A. particular species
B. interrelationship between organisms and their environment ✔

C. properties of a habitat
D. plants and animals only

Explanation:
Ecology studies interactions between organisms and environment.

36. The maximum size of a population that a given area can support is known as

A. population density
B. carrying capacity ✔

C. population growth
D. maximum population

Explanation:
Carrying capacity limits population size.

37. The producers in an aquatic food chain are

A. birds
B. phytoplankton ✔

C. zooplankton
D. fishes

Explanation:
Phytoplankton photosynthesize and produce food.

38. The frog is considered a better swimmer than the toad because it

A. has more pronounced webbed digits ✔

B. has stronger hind limbs
C. lives in water most of the time
D. is more streamlined

Explanation:
Webbed digits aid swimming.

39. Bacteria that reduce nitrates in the soil into gaseous nitrogen are called

A. nitrifying bacteria
B. denitrifying bacteria ✔

C. putrefying bacteria
D. saprophytic bacteria

Explanation:
Denitrifying bacteria complete the nitrogen cycle.

40. A pyramid of numbers is constructed by

A. comparing living and non-living things
B. measuring productivity
C. conducting census ✔

D. labeling organisms

Explanation:
It is based on counting organisms at each trophic level.