Biology
Explain the following terms:
(i) Allele
(ii) Diffusion
(iii) Photolysis
(iv) Phenotype
(v) Population density
Answer
(i) Alternative forms of a gene, occupying the same position on homologous chromosomes and depicting different forms of the same character are called alleles.
(ii) Diffusion is the free movement of molecules of a substance from the region of their higher concentration to the region of their lower concentration when the two are in direct contact.
(iii) Photolysis is the splitting of water molecules into hydrogen ions and oxygen in the presence of light.
(iv) The observable characteristics which are genetically controlled are called as phenotype.
(v) Population density is the number of individuals per square kilometre (km2) at any given time.
Related Questions
Name the following:
(i) The process of transformation of several glucose molecules into one molecule of starch.
(ii) The point of attachment of two chromatids.
(iii) The iron containing pigment in erythrocytes.
(iv) The duct which transports urine from the kidney to the urinary bladder.
(v) The part of the brain which is concerned with memory.
Given below are certain groups of terms. In each group the first pair indicates a relationship between the two terms. Rewrite and complete the second pair on a similar basis.
Example: Cytoplasm : Cytokinesis :: Nucleus : Karyokinesis.
(i) Widening of hips: Oestrogen :: Deepening of voice in males :
(ii) Brain: Meninges :: Heart :
(iii) Insulin : Beta-cells :: Glucagon :
(iv) Kidney: Renal artery :: Liver :
(v) Uterus : Implantation :: Fallopian tube :
Given below are sets of five terms each. Rewrite the terms in correct order in a logical sequence beginning with the first word that is underlined:
(i) Stimulus, Response, Receptor, Effector, Spinal cord.
(ii) Root hair, Endodermis, Epidermis, Xylem, Cortex.
(iii) Conjunctiva, Yellow spot, Pupil, Vitreous Humour, Aqueous Humour.
(iv) Australopithecus, Cro-Magnon Man, Homo erectus, Neanderthal Man, Homo sapiens.
(v) Artery, Capillaries, Venule, Vein, Arteriole
The fusion of the sperm and ovum is termed as:
- Reproduction
- Development
- Fertilization
- Embryo