Quiz 2 of 12

2020 Biology WAEC Theory Past Questions

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(a) The mechanism involved in the maintenance of balancing are as follows:
when the head is moved in any direction, the endolymph within the semi-circular canals rocks or shakes. The movement forces the sensory cells in the ampulla to set up impulses through the auditory nerve to the brain which relays the impulses to the body muscles for balancing.

(bi)    Diagram of the human ear

(bii)  Description of the Structure of the Middle Ear in Humans.

The middle ear is an air-filled chamber. It is separated from the external ear by the eardrum (tympanic membrane) and from the inner ear by oval window (fenestra ovalis).

It consists of three bones the hammer/malleus, anvil/incus, and stapes/stirrup known as ear ossicles.

The malleus is attached to the tympanic membrane/eardrum, while the stapes is in contact with the one next to it.

The Eustachian tube links the ear to the throat/pharynx.

 (a)Deficiency disease:  This is a disease caused by a lack of or inadequate supply of a specific vitamin or other nutrients/food substances.

(aii)           

(b)  procedure for chemical test for:

(i) Starch in a tuber of yam peel and slice a tuber of yam. Add a few drops of iodine to the peeled yam.
A blue-black colour is formed which indicates the presence of starch.
(ii) Glucose in orange fruit:
Cut an orange fruit and extract its juice into a beaker or test-tube.
Add a few drops of Benedict's solution or Fehling’s solutions A and B in equal volumes of the orange juice. Heat gently.
Observation:
A red/orange or brick red precipitate is formed confirming the presence of glucose.

(a)

(b) Biological basis of preserving food by:

(i) Salting: It removes water or moisture from food by osmosis, therefore, prevents microorganisms from growing on food by dehydrating and killing them.

(ii) Irradiation: This involves the exposure of food to high energy gamma rays or X-ray radiation to destroy enzymes that cause spoilage, delay the ripening of food, sprouting of vegetables, therefore, allowing long storage periods.

(iii) Smoking: Smoking reduces the water content of food thereby creating favourable conditions for microbial growth and survival known as curing. Smoke contains phenols/carbon that kill microbes on the surface of the food.

(ai) Independent Assortment of Genes

Independent assortment of genes is the random selection of genes during meiosis to produce gametes where the genes segregate as only one pair is found in any one gamete.

In dihybrid inheritance in heterozygote, the pairs of alleles are found on different pairs of chromosomes. Only four types of gametes are produced in approximately equal numbers.

(aii)     Blood Grouping in Humans:

Is determined by three alternative genes or alleles; A, B, and O. a person can only possess two alleles of the genes on a pair of homologous chromosomes.

Gene O is recessive to both genes A and B, which are co-dominant over blood group O/possess antigen A and B in the red blood cells. Hence, it is possible to have blood group A as AA (homozygous) or AO (heterozygous) and Blood group B as BB or BO. Blood group O can only exist genotypically as OO and does not possess antigen A or B in the red blood cells in the homozygous recessive state.

(b)  Classes of vertebrates in their evolutionary trend

(ai)    External Fertilization:

This involves the release of eggs by the female to the outside where the male shed its sperm on them for fertilization outside of the female.

(ii) Internal Fertilization

It involves the release of eggs inside the body of the female. The male deposit sperms inside the female, where fertilization occurs.

(bi) Groups of animals that exhibit external fertilization:

Fish/Pisces

Amphibians

(ii) Group of animals that exhibit Internal Fertilization

Reptiles, Birds or Aves, Mammals.

(ci)      Effect of Detached Placenta to a Foetus:

(ii)  Other features present in the uterus of a pregnant woman:

Umbilical cord, Amnion, Amniotic fluid, Allantois, Chorion

(d)       Dynamic Equilibrium

Nature does not encourage any population exceeding the carrying capacity of the habitat. Living organisms play a role in the regulation of the abundance, organisms or population in the habitat.

Interactions among various populations lead to competition which may result in the elimination of one species or its restriction to a non-competitive position.

Plants sometimes compete by producing toxic chemicals.

(e) Problems that Organisms in the Inter-tidal zones of Marine Habitat could encounter

(i)        Tendency of been carried away by waves

(ii)       Drying up or desiccation or exposure to air

(iii)      Oxygen deficiency

(f) Reasons the following factors are necessary for germination

(i)        Moisture

A seed imbibes or absorbs moisture causing the seed to swell and the testa becomes more permeable to oxygen and carbon(IV)oxide. The swelling will rupture the testa before germination starts.

The moisture or water activates the enzymes for metabolism leading to germination.

(ii)       Viable Seed

Viable seed has a living or healthy embryo, healthy cotyledon or endosperm, whole without boring from insect.

(g)       Reason Light Energy is Considered a Limiting Factor in the Production of Food by Autotrophs:

(a) The mechanism involved in the maintenance of balancing are as follows:
when the head is moved in any direction, the endolymph within the semi-circular canals rocks or shakes. The movement forces the sensory cells in the ampulla to set up impulses through the auditory nerve to the brain which relays the impulses to the body muscles for balancing.

(bi)    Diagram of the human ear

(bii)  Description of the Structure of the Middle Ear in Humans.

The middle ear is an air-filled chamber. It is separated from the external ear by the eardrum (tympanic membrane) and from the inner ear by oval window (fenestra ovalis).

It consists of three bones the hammer/malleus, anvil/incus, and stapes/stirrup known as ear ossicles.

The malleus is attached to the tympanic membrane/eardrum, while the stapes is in contact with the one next to it.

The Eustachian tube links the ear to the throat/pharynx.

 (a)Deficiency disease:  This is a disease caused by a lack of or inadequate supply of a specific vitamin or other nutrients/food substances.

(aii)           

(b)  procedure for chemical test for:

(i) Starch in a tuber of yam peel and slice a tuber of yam. Add a few drops of iodine to the peeled yam.
A blue-black colour is formed which indicates the presence of starch.
(ii) Glucose in orange fruit:
Cut an orange fruit and extract its juice into a beaker or test-tube.
Add a few drops of Benedict's solution or Fehling’s solutions A and B in equal volumes of the orange juice. Heat gently.
Observation:
A red/orange or brick red precipitate is formed confirming the presence of glucose.

(a)

(b) Biological basis of preserving food by:

(i) Salting: It removes water or moisture from food by osmosis, therefore, prevents microorganisms from growing on food by dehydrating and killing them.

(ii) Irradiation: This involves the exposure of food to high energy gamma rays or X-ray radiation to destroy enzymes that cause spoilage, delay the ripening of food, sprouting of vegetables, therefore, allowing long storage periods.

(iii) Smoking: Smoking reduces the water content of food thereby creating favourable conditions for microbial growth and survival known as curing. Smoke contains phenols/carbon that kill microbes on the surface of the food.

(ai) Independent Assortment of Genes

Independent assortment of genes is the random selection of genes during meiosis to produce gametes where the genes segregate as only one pair is found in any one gamete.

In dihybrid inheritance in heterozygote, the pairs of alleles are found on different pairs of chromosomes. Only four types of gametes are produced in approximately equal numbers.

(aii)     Blood Grouping in Humans:

Is determined by three alternative genes or alleles; A, B, and O. a person can only possess two alleles of the genes on a pair of homologous chromosomes.

Gene O is recessive to both genes A and B, which are co-dominant over blood group O/possess antigen A and B in the red blood cells. Hence, it is possible to have blood group A as AA (homozygous) or AO (heterozygous) and Blood group B as BB or BO. Blood group O can only exist genotypically as OO and does not possess antigen A or B in the red blood cells in the homozygous recessive state.

(b)  Classes of vertebrates in their evolutionary trend

(ai)    External Fertilization:

This involves the release of eggs by the female to the outside where the male shed its sperm on them for fertilization outside of the female.

(ii) Internal Fertilization

It involves the release of eggs inside the body of the female. The male deposit sperms inside the female, where fertilization occurs.

(bi) Groups of animals that exhibit external fertilization:

Fish/Pisces

Amphibians

(ii) Group of animals that exhibit Internal Fertilization

Reptiles, Birds or Aves, Mammals.

(ci)      Effect of Detached Placenta to a Foetus:

(ii)  Other features present in the uterus of a pregnant woman:

Umbilical cord, Amnion, Amniotic fluid, Allantois, Chorion

(d)       Dynamic Equilibrium

Nature does not encourage any population exceeding the carrying capacity of the habitat. Living organisms play a role in the regulation of the abundance, organisms or population in the habitat.

Interactions among various populations lead to competition which may result in the elimination of one species or its restriction to a non-competitive position.

Plants sometimes compete by producing toxic chemicals.

(e) Problems that Organisms in the Inter-tidal zones of Marine Habitat could encounter

(i)        Tendency of been carried away by waves

(ii)       Drying up or desiccation or exposure to air

(iii)      Oxygen deficiency

(f) Reasons the following factors are necessary for germination

(i)        Moisture

A seed imbibes or absorbs moisture causing the seed to swell and the testa becomes more permeable to oxygen and carbon(IV)oxide. The swelling will rupture the testa before germination starts.

The moisture or water activates the enzymes for metabolism leading to germination.

(ii)       Viable Seed

Viable seed has a living or healthy embryo, healthy cotyledon or endosperm, whole without boring from insect.

(g)       Reason Light Energy is Considered a Limiting Factor in the Production of Food by Autotrophs: