When synthesizing a strand of double-stranded DNA, which of the following could be a plausible combination of nitrogen bases?

• A. 28% Adenine, 22% cytosine, 22% guanine, 28% thymine
• B. 23% Adenine, 23% cytosine, 27% guanine, 27% uracil
• C. 48% Adenine, 52% cytosine, 52% guanine, 48% thymine
• D. 24% Adenine, 24% cytosine, 26% guanine, 26% thymine

Which of the following pairs of organisms exist as colonies?

• A. Obelia and Euglena
• B. Pandorina and Volvox
• C. Chlamydomonas and Amoeba
• D. Hydra and Spirogyra

Which of the following statements about the circulation of water in nature is not correct? Water

• A. constantly evaporates from seas, rivers, lakes and soil
• B. vapour rises, cools, condenses and precipitates as rain and dew
• C. removed from ocean is permanently lost
• D. is lost in plants by transpiratin and decay

Which of the following blood vessels carries oxygenated blood away from the heart?

• A. Arteries
• B. Venules
• C. Capillaries
• D. Veins

The animals that move by means of flagella include

• A. Chlamydomonas and Euglena
• B. Planeria and Amoeba
• C. Amoeba and Hydra
• D. Paramecium and Planeria

Which of the following is NOT an excretory product of animals?

• A. carbondioxide
• B. urea
• C. sweat
• D. oxygen

The biological association that contributes directly to succession in a community is

• A. competition
• B. predation
• C. parasitism
• D. commensalism

Which of the following associations is an example of mutualism

• A. hydra viridis and zoochlorellae
• B. human and lice
• C. shark and remora fish
• D. bread and rhizopus stolonifer

The following are abiotic components of an ecosystem except

• A. temperature
• B. oxygen
• C. bacteria
• D. soil

Which of the following characteristics differentiates a palisade cell from a liver cell? The possession of

• A. a cell wall and a cytoplasm
• B. a vacuole and a nucleus
• C. non-cell membrane and chloroplast
• D. a cell wall and chloroplast