Long Answer Type(a) Mention the important features of the Neanderthal man.
(b) What are homologous organs? How do they help in providing evidence for organic evolution?
a. Describe the different types of vascular bundles.
b. Give three anatomical differences between a monocot root and a dicot root.
c. Explain the effect of light and temperature on photosynthesis.
(a) Explain the transpiration pull theory for ascent of sap.
(b) Explain the process of spermatogenesis in humans.
(c) Define the following:
(i) Placentation
(ii) Parthenocarpy
(iii) Diffusion
a. Transpirational theory was proposed by Dixon and Jolly. The theory states that water lost from mesophyll cells by transpiration. The DPD increases in mesophyll cells due to loss of water causing cells to absorb water from neighbouring cellsby the process of endosmosis. The OP increase and water potential decreases. In turn, water is absorbed from xylem. The continuous water column set up due to cohesion and adhesion. Thus a suction pressure is developed which is called the transpirational pull. The continuous water column and the pull makes the roots to absorb water.
b. Spermatogenesis in humans: Formation of Spermatid:
Multiplication phase/division: undifferentiated germ cells arise by mitotic division of primordial germ cells to form spermatogonia or sperm mother cells. These undergo mitosis to form supermatogonia which move towards the lumen of seminiferous tubules and enter growth phase. These cells are called spermatocytes.
Growth phase: Spermatocytes grow in size, accumulate nutrients and replicate DNA. They are now called primary spermatocytes.
Maturation phase: Each primary spermatocyte undergoes first maturation division/meiosis and two haploid cells are formed. These are called secondary spermatocytes. They undergo a further second mitotic division to form 4 spermatids.
Spermiogenesis:
Nucleus shrinks with closely packed DNA.
Formation of acrosome takes place.
The axial filament is formed from distal centriole.
Mitochondrial spiral is formed from mitochondria.
Loss of cytoplasm, just a sheath remains around mitochondria.
(c)
(i) Placentation is the arrangement of ovules within the ovary and the formation of placenta in animals and the arrangement of placenta along ovarian wall.
(ii) Parthenocarpy: Phenomenon of development of fruits without fertilization.
(iii) Diffusion: Movement of molecules of a substance from its higher concentration to its lower concentration.
(a) Why are xylem and phloem classified as complex tissues? Describe the structure of phloem.
(b) Describe the ultra-structure of chloroplast.
(c) State three functions of the placenta.
(a) Describe the experiment performed by Griffith. What conclusions did he infer from his observations?
(b) What is artificial insemination? Mention two ways in which it is useful in breeding of dairy animals.
(c) What is single cell protein? Give its source and significance.
(a) How did Hershey and Chase prove that DNA is the genetic material?
(b) Give one main application of each of the following:
(i) MRI
(ii) Ultrasound
(iii) ECG
(c) Explain the role of stem cells in medical treatment.
(a) Write short notes on:
(i) Multiple Alleles
(ii) Artificial measures to control population
(b) What complications will arise if the blood of an Rh positive person is transfused to an Rh negative person and vice versa?
(c) State any three goals of the human genome project.
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