IGCSE Biology Paper-1: Specimen Questions with Answers 166 - 167 of 208

Question 166

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Question

MCQ▾

An organism with two identical alleles is

Choices

Choice (4)
a.Dominant
b.Heterozygous
c.Homozygous
d.Hybrid

Answer

c.

Explanation

  • Allele or Allelomorph: Ex: Contrasting forms of a gene which are found on the same locus in the two homologous chromosomes & control the expression of a trait are called alleles. Tallness (T) and dwarfness (t).
  • Homozygous: It is an individual which contains identical alleles of a gene or factor of a character on its homologous chromosome Ex: TT and tt
  • Heterozygous: Ex: It is an individual which contains the two-contrasting factor of a character or two different alleles of a gene on its homologous chromosomes. Tt

Question 167

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Question

MCQ▾

The diagram shows someone blowing up a balloon.

The Gas in the Balloon is Carbon Dioxide

The Gas in the Balloon is Carbon Dioxide

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What percentage of the gas in the balloon is carbon dioxide?

Choices

Choice (4)
a.0.4 %
b.40 %
c.4.0 %
d.0.04 %

Answer

c.

Explanation

Partial pressure of a gas is the pressure it exerts in a mixture of gases and is equal to the total pressure of the mixture divided by percentage of that gas in the mixture. For instance, if the pressure of atmospheric air at sea level is 760 mm. Of mercury (Hg) and oxygen forms 21 % of the air, the partial pressure of oxygen will be 21 % of 760, or 159 mm. Hg. In other words, the partial pressure of a gas is proportional to its concentration in the mixture. Only about 0.3 ml. of can dissolve in 100 ml. of plasma, about 20 ml. of is carried by hemoglobin in 100 ml. of blood. In atmospheric air except these gases some traces of helium, argon and neon are also found.

Partial pressures of respiratory gases in mm. Hg

Partial pressures of respiratory gases in mm. HgPartial pressures of respiratory gases in mm. Hg
GasInspired airAlveolar airVenous bloodArterial bloodExpired airTissue cells
Oxygen158100 – 1054095 – 10011620 – 40
Carbon dioxide0.34046403245 – 52
Nitrogen596573573573565

Composition of three samples of air

Composition of three samples of airComposition of three samples of air
GasesInspired airExpired airAlveolar airGain/loss %
Oxygen20.84%15.70%13.6%Gain 5.14%
Carbon dioxide0.04%4.00%5.3%Loss 3.96%
Nitrogen78.62%74.50%74.9%Gain 4.12%
Water0.5%6.2%6.2%Loss 5.7%