Q.58 "Eutrophication" is a natural ageing of a lake.

CBSE 2011, 2012][21

Mention another feature which defines this term.

Eutrophication: Algae reduces the concentration of dissolved oxygen in water. This process is known as eutrophication. It retards the development of fish which takes oxygen from water. In a young lake, the water is and introduction of nutrients such as nitrogen and-phosphorus which encourage the growth of aquaticorganisms in it. As the lake's fertility increases, plant and animals life begin to develope and their death all lake bottom.

Over the centuries, as silt and organic debris pile up, the lake grows shallower and warmer. Now the warm water organisms replace those that live in a cold environment. 
Marsh plants tal:e root in the shallows and begin to fill in the original lake basin and the lake develops large masses of floating plants finally converting into land.

.67 Fertilizers and pesticides act as polltants'.

Ans The two types of agrochemicals are pesticides and Comment on the statement. fertilizers. They not only change chemical properties of soil, but also effect soil organisms, surface water and ground water resources.

Pesticides are chemicals used in killing pathogens pests and unwanted growth in agriculture, horticulture, forestry and water. They chemically chlorinated hydrocarbons, organophosphates, metallic salts, and acetic acid derivatives. Many of them are nonbiodegradable. Most pesticides are broad spectrum, killing most of the organism. Some of them even adversely affect the useful organisms in later stages. Pesticides cause soil pollution by becoming part of soil ecosystem.

Fertilizers are chemicals used to increase the fertility of soil. Excessive use of fertilizers cause soil deterioration through decrease of natural microflora leaching down of fertilizers cause pollution of underground water. Parts of fertilizers added to crop fields are passed down into water bodies and bring about eutrophication. Salts entering the crop plants in excess may prove harmful.down of cause pollution of underground water. Parts of fertilizers added to crop fields are passed down into water bodies and bring about eutrophication. Salts

entering the crop plants in excess may prove harmful.

The neriod from birth to the natural death of an organism.

Types of Reproduction

somatic pa

13.The develo

parent plan

1Reproductive System is a system of organs and processes

that take part in reproduction.

Exual kep

2. Reproduction is the formation of new similar young living

14. Sexual Rep

ones are fo

gametes. Se

a) Syngam

Zygote.

protist=

metazoa

b) Conjug

exchang

and bac

c) Isogam

morpho

d) Anisoga

are diss

in size

microg

Size, no

macrog

15.Sexual repr

or amphigor

16. Sexual rep

fertilization

17.Sexual Repr

i) It causes

it) It cause

iin) It cause c

iv) Cause ew

v) It involve

18. Sexual repro

require lots c

ones die due

organism by grown up individual of species or race.

3, Animal reproduction is of two types: a) Asexual b) Sexual

4. Asexual Reproduction: Mode of reproduction or formation

of new young Individual from a specialised or unspecialised

part of single parent without formation and fusion of gametes.

5. Asexual reproduction occurs by the following methods:

Fission: In this type, body of an individual undergoes division

eries

to produce two or more equal-sized daughter cells.

a) Binary fission: The mature individual divides into two

equal-sized daughter individual. It may be simple (can

e

occur in any plane e.g., in Amoeba)

b) Multiple fission: Formation of numbers of small daughters

by division of parent e.g, Plasmodium, Monocystis.

c) Plasmotomy: Cleavage of protoplasm or multinucleated

body into multinucleated parts e.g., Opalina, Pelomyxa.

d) Cysts and spores These are minute propagules which

function as disseminules as well as perenating structures.

e.g, Amoeba, Plasmodium etc.

e) Budding: Mode of asexual reproduction in which new

organism develops as out growth or bud from a parent. It

ii) Exogenous

is of two types : i) Endogenous

) Fragmentation: Breakdown of individual's body

externally or internally. e.g, Spirogyra, starfish.

ch

6. Bulbils are fleshy buds covered by leaves.

.Turions are fleshy buds developed in an aquatic plant.

. Stem cuttings are common in Citrus, Rose, Sugarcane,

Coffee etc. It can be induced by dipping the cuttings in NAA,

9. A layering is very common in Litchi, China rose,

IBA, IAA etc.

romegranate etc. It is promoted by adding water, IAA and IBA.

0.Grafting is common in dicots as they possess cambium. it

1S absent in monocots as they lack cambium.