17. Describe the three domains of life.
3
18. Explain the chemical events that take place to form a blood clot
to seal the wound.
3
19. Describe the three common steps in the sexual reproduction of
fungi.
3
20. How does the condition of erythroblastosis foetalis results in a
new born baby?
3
21. Justify the statement “Mammals are the most successful and
dominant animals today”.
3
22. Write the economic importance of Lichens.
3
23. Differentiate between cartilaginous and bony fishes. Give
example of each.
5
24. What is meant by living? Give any four defining features of
life forms.
1+4=5
Answers
Answer:
17. The three domains are the Archaea, the Bacteria, and the Eukarya. Prokaryotic organisms belong either to the domain Archaea or the domain Bacteria; organisms with eukaryotic cells belong to the domain Eukarya.
18. A platelet plug is formed, and the external bleeding stops. Next, small molecules, called clotting factors, cause strands of blood-borne materials, called fibrin, to stick together and seal the inside of the wound. Eventually, the cut blood vessel heals and the blood clot dissolves after a few day
19. Sexual reproduction in the fungi consists of three sequential stages: plasmogamy, karyogamy, and meiosis. The diploid chromosomes are pulled apart into two daughter cells, each containing a single set of chromosomes (a haploid state). The cell formed by karyogamy is called the zygote.
20. Erythroblastosis fetalis destroys red blood cells
Destruction of the red blood cells (hemolysis) can be rapid in a fetus. As a result, the fetus will not receive enough oxygen, which may lead to anemia, other illnesses, or even death.
21. The mammals are the most successful and dominant animals today. They thrive very well in most environment of the world - polar ice caps, deserts, oceans, mountains, forests, grasslands and dark-caves.Unique mammalian characteristics are : (a) Body covered with hair.
22. Economic importance of lichens is as follows: They are a good pollution indicators. They do not grow in polluted areas. They grow on rocks and release some chemicals that can disintegrate rocks and this results in rock weathering.
23. As the name suggests, “bony fish” have a skeleton composed of only bones while a cartilaginous fish has a skeleton made entirely of cartilage.
24. Four defining features of life forms are: (a) Growth: It is the permanent increase in cell number and size of the organism.(c) Metabolism : The sum total of all the chemical reactions occurring in the body of an organism is metabolism. No non-living object exhibits metabolism.
Answer:
17 . Three domain of life are the Archaea, the Bacteria, and the Eukarya. Prokaryotic organisms belong either to the domain Archaea or the domain Bacteria; organisms with eukaryotic cells belong to the domain Eukarya
18.A platelet plug is formed, and the external bleeding stops. Next, small molecules, called clotting factors, cause strands of blood-borne materials, called fibrin, to stick together and seal the inside of the wound. Eventually, the cut blood vessel heals and the blood clot dissolves after a few days.