biology class X notes sindh board

CHAPTER 7

MAN AND HIS ENVIRONMENT
Short Questions Answers

What is the effect of light on ecosystem?

EFFECT OF LIGHT ON ECOSYSTEM

Light affects organisms in three ways:

1. Intensity of light,
2. Its duration or photoperiod and
3. Its quality Or Type (wave length).

Intensity of Light:

• In plants intense light may destroy the chlorophyll.
• It also affects opening and closing of the stomata.
• In animals light affects development of pigments.

Exposure time of light (Photoperiod):

• Light is also necessary for vision.
• Duration of light (photoperiod) affects starts of certain biological processes.
• Making Vitamin D in human being.

Quality of Light:

• Out of seven colors of visible light (electromagnetic spectrum), chlorophyll absorbs only red and blue light for photosynthesis.
• Most of the light reaching the earth is converted to heat and thus light also maintains the temperature of the earth and atmosphere in the ecosystem.

  Which one is the first trophic level of ecosystem and how?

TROPHIC LEVELS

The steps of transfer of energy rich food are called trophic levels.

 FIRST TROPHIC LEVEL OF ECOSYSTEM

PRODUCERS:

• Producers always occupy the first trophic level in any food chain because only producers have the ability to trap solar energy with the help of chlorophyll and synthesis their own food.
• The producers produce food for themselves and other organisms of ecosystem.
• They are primary source of energy for other organisms.
• All members of community depend, directly or indirectly on the producers for their food and energy.

What do we mean by nitrogen fixation and how it occurs in an ecosystem?

NITROGEN FIXATION:

“Conversion of atmospheric free nitrogen gas into soluble nitrogen compounds (nitrates) is called nitrogen fixation.”

Nitrogen Fixation Occurs In Ecosystem:

The atmosphere contains about 78 percent nitrogen gas. It is an inert gas and the organisms cannot use it directly. Therefore, nitrogen is first changed to soluble nitrogen compounds such as nitrates (NO₃) which the plants can absorb from the soil.

What is interaction?

INTERACTION IN ECOSYSTEM

The organisms in an ecosystem not only interact with their physical environment but also with each other. These interaction maintain balance in growth and population. These interactions may be beneficial or harmful.

Define symbiosis and also describe its types?

SYMBIOSIS

Generally the symbiosis is defined as an association between two living organisms of different species for mutual benefit or in which one partner gets the benefit and the other is neither benefited nor harmed.
In other words none of the two partners is harmed.

Types Of Symbiosis:

There are three types of symbiosis

1. Parasitism:

   Parasitism is an association between two living organisms in which one lives in or on the body of the other and derives nourishment from it..
   They have rapid rate of reproduction.

2. Commensalism:
   

   It is an association between two living organism of different species in which one is benefited and the other is not affected, that is it is neither benefited nor harmed.

3. Mutualism:

   It is an association between two species of living organisms for mutual benefit.
   The two partners are dependent on each other for their survival and growth.

What is pyramid of number?

PYRAMID OF NUMBERS

The pyramid of numbers was advanced by Charles Elton in 1927. It is define as:

“A pyramid of numbers is a graphical representation of members of population in an area at different in trophic level.”

It is an upright pyramid in light of the fact that in an ecosystem, the producers are always more in number than other trophic levels.

 What is greenhouse effect?

GREEN HOUSE EFFECT

Green House Gases

CO₂ and methane produced during burning of fossil fuels in urban areas are generally called greenhouse gases.

Global Warming OR Green House Effect:

Due to excessive burning of fossil fuels, the amount of CO₂ in atmosphere becomes abnormally high. CO₂ and methane if produced in high quantity in atmosphere are accumulated below the ozone layer, which do not allow heat energy of sun to reflect back in space. As a result, heat remains within the earth’s atmosphere this phenomenon is called global warming or greenhouse effect.

 What is algal bloom and how it destroy the life of an aquatic ecosystem?

EUTROPHICATION OR ALGAL BLOOM

Growth of algae with very high rate due to increase in phosphorous and nitrogen compounds is called algal bloom or eutrophication. They accumulate in water reservoirs and promote algal growth up to dangerous level i.e. algal bloom.

Effects on Aquatic ecosystem:

• Algal bloom when floats on water surface spoil fishing, swimming and recreational qualities of water.
• As the algae die, the activity of decomposers increase and they consume more and more oxygen. Deficiency of oxygen results in massive death of useful organisms such as fishes.

 What measure can be taken to control water pollution?

CONTROL OF WATER POLLUTION

• Public awareness at all levels is important. It should be through social media, political leaders, institution from pre-primary level.
• Strict legislation and implementation is required on sewage treatment and industrial recycling processes.
• No industrial and agricultural waste should be added to water bodies before complete treatment.

 Write down the name of some endangered mammals of Pakistan.

 ENDANGERED MAMMALS OF PAKISTAN

• Punjab Urial
• Markhor
• Snow Leopard
• Asia sandpit green turtle
• Indus river dolphin
• Bear of Deosai

Draw the diagram of nitrogen cycle.
Write down the name of some endangered birds of Pakistan.
ENDANGERED BIRDS OF PAKISTAN:

• Siberian Crane
• Falcon
• Cheer Pheasant
• Chacor
• Long Billed Vulture
• Red Avadavar

 Illustrate acid rain and its effect?
ACID RAIN

Acid rain includes any form of precipitation with acidic components, such as sulphuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic.

Effect:
The acid destroy soil, micro-organisms of soil, skin of animals, building material.

What is meant by depletion of ozone layer?
DEPLETION OF OZONE LAYER

Scientist have found ozone layer is gradually depleting (getting thin) due to chloro flouro carbon (CFC), as they react with ozone and convert it into O₂.
The CFC used as propellant in pressurized aerosol, foaming agent, refrigerators etc. Each one atom of chlorine converts more than 100000 molecules of ozone O₃ to Oxygen O₂.

Draw diagram for sewage treatment?