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.
