Biology_2018_STPM term 3_Objectives

Which of the following statements define species?

Ⅰ. A group of organisms that share a common ancestor, forming several branches on the evolutionary tree.

Ⅱ. A group of organisms that share diverse morphological, structural and functional characteristics.

Ⅲ. A group of organisms that are capable of interbreeding and producing fertile offspring.

Ⅳ. A group of organisms that share the same ecological niche.

• Ⅰ and Ⅱ

• Ⅰ and Ⅳ

• Ⅱ and Ⅲ

• Ⅲ and Ⅳ

Answer explanation

The biological definition of species is that they are a group of organisms that share common characteristics and are capable of interbreeding and producing fertile offspring. A habitat has different species but each species has its own ecological niche.

To protect the endangered species of flora and fauna, the government has assigned in the establishment of the following conservation parks:

Ⅰ. The National Elephant Conservation Centre in Kuala Gandah, Pahang

Ⅱ. The Marine Park in Payar Island, Kedah

Ⅲ. The Royal Belum Forest Reserve in Banding, Perak

Ⅳ. The Sepilok Orang Utan Rehabilitation Centre in Sandakan, Sabah

Which parks correspond correctly to the in situ and ex situ conservation?

• ex situ : Ⅰ , Ⅱ

  in situ : Ⅲ , Ⅳ

• ex situ : Ⅰ , Ⅳ

  in situ : Ⅱ , Ⅲ

• ex situ : Ⅱ , Ⅲ

  in situ : Ⅰ , Ⅳ

• ex situ : Ⅲ , Ⅳ

  in situ : Ⅰ , Ⅱ

Answer explanation

Ex situ conservation is the preservation of organisms outside their natural habitats. This involves conservation of genetic resources, wild and cultivated species of organisms. In situ conservation is conservation of organisms in their natural habitats.

What is the characteristics of an organism that shows a high biotic potential?

• Cares for the young

• Has a short life cycle

• Has a small number of progenny

• Does not show mating behavior

Answer explanation

Biotic potential is the capacity of organisms to reproduce and increase in numbers under optimal conditions. Organisms that have high biotic potential are typically small, have a short live span, occupy unpredictable environments and have a high reproductive potential that produce lots of small offspring early in their life cycle.

Which compound is utilised as the energy source by heterotrophs in the carbon cycle?

• Phosphate

• Carbon dioxide

• Organic molecules

• Inorganic molecules

Answer explanation

Heterotrophs cannot synthesises their own food. They obtain food and energy from consuming other organic substances such as plants and animals. Organic molecules contain carbon.

The energy flow in one community is shown in the flow chart.

Which statement is true about the energy flow above?

• S undergoes photosynthesis.

• Q is the light energy being reflected.

• P converts sunlight into chemical energy.

• R is mostly lost in the form of faeces and excretion.

Answer explanation

All the energy from the sun do not reach the Earth. 34% is reflected back to space by clouds. The Earth itself reflects 66% back to space. Less than 1% of the total energy that reaches the Earth is used by plants for photosynthesis. S does not undergo photosynthesis because herbivores are heterotrophs. P converts solar energy to chemical energy and plants do not produce faeces and excretions as animals do.

Which are true about continuous variation?

Ⅰ. Shows a discrete distribution

Ⅱ. The characteristics that can be measured

Ⅲ. Not affected by environmental factors

Ⅳ. Two or more genes control the same characteristics

• Ⅰ and Ⅱ

• Ⅰ and Ⅳ

• Ⅱ and Ⅲ

• Ⅱ and Ⅳ

Answer explanation

Continuous variation shows a complete range of characteristics ranging from one extreme to another. These characteristics can be measured, such as height and weight of a number of individuals. These characteristics are affected by several combined genes and can be influenced by environmental factors. They show a normal distribution.

A group of students uses four quadrants to investigate the population of plant Q in a field. The results of the sampling are shown in the table.

Calculate the size of the quadrant if the species density of plant Q is 0.75?

• 0.5 m × 0.5 m

• 1.0 m × 1.0 m

• 1.5 m × 1.5 m

• 2.0 m × 2.0 m

Answer explanation

Several population of a bird species have migrated to various new habitats and evolved in response to the different environmental pressure of each habitat. What is the type of speciation that has occurred?

• Adaptive radiation

• Hybridisation

• Genetic drift

• Isolation

Answer explanation

Adaptive radiation occurs when a small group of ancestral species rapidly diversifies into a large number of descendant species. One of the factors that can trigger an adaptive radiation is an ecological opportunity in new habitats where new resources are available in abundance. This open new environmental niches for the organisms as they face various selection pressures and new challenges and evolve into new species.

The pedigree diagram of a family affected with a recessive disease is shown.

Which statements are true about the pedigree shown?

Ⅰ. The gene for the trait is autosomal.

Ⅱ. U and W are homozygous recessive.

Ⅲ. R is homozygous dominant.

Ⅳ. T and V are carriers.

• Ⅰ and Ⅱ

• Ⅰ and Ⅳ

• Ⅱ and Ⅲ

• Ⅲ and Ⅳ

Answer explanation

Since both male and female children are affected and the parents are normal, each child has inherited one recessive trait from both parents. Therefore, R is heterozygous. The trait is not sex-linked because in a sex-linked disease, the father has to carry the recessive allele in order to pass the allele to the daughter who has the disease. Therefore the disease is autosomal and not sex-linked. In autosomal recessive conditions, the affected individuals must be homozygous recessive. T and V may be carriers or may not carriers depending on the probability of them being either homozygous dominant or heterozygous.

In Hardy-Weinberg equilibrium, 36% of individuals in a population of birds show the recessive phenotype. What is the frequency of the dominant allele in the population?

• 0.36

• 0.41

• 0.60

• 0.64