Question 1

The diagram shows how Homo sapiens (modern people) could have evolved from earlier ancestors.Which statement about modern people and their ancestors is correct?

Accepted Answer

All the organisms are given binomial nomenclature in which the first word is the genus and the second the species. In the above, example it is seen that the first name Homo is common and the second is the species, thus all of them belong to the same genus but not the same species.

Question 2

The diagram shows two experiments investigating gas exchange in small aerobic crustaceans.Soda lime absorbs carbon dioxide. Which way does the liquid marker move?

Accepted Answer

Crustaceans breath oxygen, as does (nearly) every other creature on earth. As they are aquatic creatures, they use the same respiratory system as fish and breath oxygen through gills. The diagram shows the apparatus that can be used to investigate the exchange of gases/respiration in small aerobic crustaceans. Carbon dioxide is produced by the process of respiration and affects the volume and pressure of gas in the tube.In tube P, O2​ is taken in and CO2​ released by crustaceans, is absorbed by soda lime reducing the pressure exerted by the gas. Hence, liquid marker moves to left.Whereas in tube Q, glass beads are present instead of soda lime, so there is no absorption of CO2​, the pressure exerted by CO2​ here is balanced by that of oxygen and hence the liquid marker stood still.

Question 3

Yeast is placed inside a container full of a glucose solution with no air.Which word equation summarizes the process that takes place inside the container?

Accepted Answer

Yeast can respire both aerobically and anaerobically. When yeast is placed inside a container full of glucose solution with no air it undergoes anaerobic respiration and produces carbon dioxide and ethanol.

Question 4

Which substances are excreted by humans?

Accepted Answer

The waste products produced in humans are carbon dioxide, urea and excess water (in the form of urine).

Question 5

The diagram shows a simple reflex arc. Which labelled part is the sensory neurone?

Accepted Answer

Reflex arc refers to the pathway through which a reflex travels from the site of stimulus to sensory neuron to motor neuron to reflex muscle movement. A sensory neuron functions to carry the stimulus from the receptor site whereas a motor neuron carries signals to a muscle or organ for reflex action. In the given diagram A is the receptor, B is sensory neuron, C is a Synapse and D is an effector muscle connected to a motor neuron.

Question 6

Some structures in the eye are listed.1 cornea2 iris3 lens4 retinaWhich structures contain light receptors?

Accepted Answer

The retina of eye contains two types of light receptors: cones and rods. These cells receive and organize visual information. 
Cornea is the clear outer layer at the front of the eye. It helps the eye to focus light so the vision is clear. 
Iris is the colored tissue at the front of the eye that contains the pupil in the center. The iris helps control the size of the pupil to let more or less light into the eye.
Lens of an eye is a curved structure that bends light and focuses it for the retina to help see images clearly.

Question 7

In humans, what is an example of a secondary sexual characteristic in both males and females?

Accepted Answer

. Hair growth on face is the secondary sexual characteristic in males.. broadening of hips and fat deposition on the hips and thighs is the secondary sexual characteristic in females.. Sexual organs growth is a secondary sexual characteristic in both males and females

Question 8

Which contraceptive method could provide protection from sexually transmitted infections?

Accepted Answer

. Condoms are the only form of contraception that protect against most STIs as well as preventing pregnancy. . A diaphragm is inserted inside the vagina to stop sperm from getting in. They do not protect against STIs.. Hormone implant placed under the skin in your upper arm by a doctor or nurse. It releases the hormone progestogen into your bloodstream to prevent pregnancy. It does not provide protection from STIs.. Vasectomy do not protect  from STIs. Semen can still carry STDs, even if it doesn’t contain sperm.

Question 9

Which human characteristics are inherited?

Accepted Answer

. Earlobe attachment and shape are inherited. This happens due to the influence of a dominant allele. If the parents' genes express the dominant allele, the child will be born with free earlobes.. Eye colour is inherited. It is determined by variations in a person's genes. In the most elementary form, the inheritance of eye color is classified as a Mendelian trait.. Languages are learned, not inherited via the genes. All languages change during the course of time, and the longer the time period the greater the changes.. Skin colour is inherited. Differences in skin color among individuals is caused by variation in pigmentation, which is the result of genetics.

Question 10

A rabbit has 44 chromosomes in each of its body cells. Which row correctly describes the gamete cells?

Accepted Answer

As given in the question, the number of chromosomes in somatic cells of rabbit is 44 (2n), so the number of chromosomes in gametes will be 22 (n). This is due to fact that in normal somatic (body) cells, the chromosomes exist in pairs. The condition is called diploidy. During meiosis the cell produces gametes, or germ cells, each containing half the normal or somatic number of chromosomes. From this it is also clear that gametes are genetically different from somatic cells.Hence, option B is correct.

Question 11

Which definition of continuous variation is correct?

Accepted Answer

For any species, a characteristic that changes gradually over a range of values and that results in a range of phenotypes between two extremes shows continuous variation. For example- Height ranges from that of the shortest person in the world to that of the tallest person. Any height is possible between these two extremes. So, it is continuous variation.

Question 12

When is evolution by natural selection most likely to occur?

Accepted Answer

Natural selection occurs when individuals with certain genotypes are more likely than individuals with other genotypes to survive and reproduce, and thus to pass on their alleles to the next generation. As Charles Darwin (1859) argued in "On the Origin of Species", if the following conditions are met, natural selection must occur:1) There is variation among individuals within a population in some trait.2) This variation is heritable (i.e., there is a genetic basis to the variation, such that offspring tend to resemble their parents in this trait).3) Variation in this trait is associated with variation in fitness (the average net reproduction of individuals with a given genotype relative to that of individuals with other genotypes).Hence option D is correct.If the environmental conditions are stable or if there is a stable population of predators, then there will be no selection pressure. Therefore option A, B and C are incorrect.

Question 13

What process uses the principal source of energy input to biological systems?

Accepted Answer

. The Sun is the principal source of energy input to biological systems. Sunlight allows plants, algae and cyanobacteria to use photosynthesis to convert carbon dioxide and water into organic compounds like carbohydrates. This process is the fundamental source of organic material in the biosphere.

Question 14

The diagram shows an aquatic food web. Which statement is correct?

Accepted Answer

In the given food web, phytoplankton and sea weeds are the two primary producers. As zooplankton, krill and crab directly feed on producers (plants), so they are termed as primary consumers or herbivores.  Fish, blue whale and squid are the secondary consumers (as they feed on primary consumers). Seagull and seal feed on secondary consumers and hence are termed as tertiary consumers. Therefore, in the given food web there are two producers, three herbivores (primary consumers), three secondary consumers and two tertiary consumers. So we can say that option A is correct.

Question 15

Why are bacteria useful in biotechnology and genetic engineering?

Accepted Answer

Genetic engineering (also called genetic modification) is a process that uses laboratory-based technologies to alter the DNA makeup of an organism. The advantages of using bacteria for biotechnology and genetic engineering include their simple non-compartmented structure, the accessibility of their genetic material, and the fact that bacteria are among the fastest reproducing organisms in the world, doubling every 4 to 20 minutes. For example, the bacterium Escherichia coli can divide every 20 min in the laboratory under aerobic, nutrient-rich conditions.

Question 16

What is a description of genetic engineering?

Accepted Answer

Genetic engineering, also called recombinant DNA technology, involves the group of techniques used to cut up and join together genetic material, especially DNA from different biological species, and to introduce the resulting hybrid DNA into an organism in order to form new combinations of heritable genetic material.Cross breeding individuals with different characteristics (such as recessive alleles) is termed as hybridisation. Whereas selecting random mutations to produce new varieties is called mutational breeding. Hence, option C is correct, while A, B and D are incorrect.

Question 17

Large areas of tropical forests have been cleared to grow monocultures of palm oil plants.
Which effect will this have on the ecosystem?

Accepted Answer

Clearing tropical forest will result in large scale habitat loss for variety of species like elephants, tigers and orangutans. Such act will lead to the decreasing of species varieties in that particular area.

Question 18

The diagram shows how Homo sapiens (modern people) could have evolved from earlier ancestors. Which statement about modern people and their ancestors is correct?

Accepted Answer

A scientific name is designed for the universal identity of an organism and it generally follows the binomial nomenclature method. In binomial nomenclature the first part denotes the genus of the organism, and the second part denotes the species name of the organism. 
For instance, Homo sapiens for human. Here Homo is the genus and sapiens is the species. 
So in the given diagram Homo sapiens, Homo heidelbergensis, Homo erectus, and Homo habilis all of them belong to the same genus but different species.

Question 19

The diagram shows how sewage is treated. Why is air bubbled through the aeration tank?

Accepted Answer

Wastewater aeration is the process of adding air into wastewater to allow aerobic bio-degradation of the pollutant components. Aeration in an activated sludge process is based on pumping air into a tank, which promotes the microbial growth in the wastewater. Aeration provides oxygen to bacteria for treating and stabilizing the wastewater. Oxygen is needed by the bacteria to reproduce quickly and allow biodegradation to occur. The supplied oxygen is utilised by bacteria in the wastewater to break down the organic matter containing carbon to form carbon dioxide and water. The microbes feed on the organic material, forming flocks which can easily settle out. After settling in a separate settling tank, bacteria forming the "activated sludge" flocks are continually recirculated back to the aeration basin to increase the rate of decomposition.Hence, option A is correct.

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