BIO(Ecosystems)

                   Ecosystems

         Let us discuss these questions

What is a habitat?

Is a tree habitat only for a crow?

In what way an ecosystem is different

from habitat?

We found that there were differences

between the ecosystems of land and water

and different ecosystems on land and water

as well. We can see differences within

ecosystems in very small areas as well.

We have studied in the chapter 'habitat' about 

the variations in the living

communities, as well as organisms

present at different levels, in the pond

ecosystem and the tree. In this chapter we

will see how organisms have started

inhabiting certain areas, what needs they

have and how they acquire different

conditions from their surroundings to meet

them.

                   Mangroves

To adjust themselves to diverse and

distinct changes in ecosystems, organisms

have to adapt different means for better

survival. For example, some trees such as

Mangroves like Avicennia have evolved a

curious way to deal with the problems of

growing in a wet and salty place. They have

evolved to have curious looking

These “knees” (aerial roots) develop

from the lateral roots that are growing near

the surface, and protrude up to 12 inches

out of the soil or sediment. The precise

function of these “knees” is not definitely

known, but there is general agreement that

they aid the plants in maintaining adequate

root respiration in a watery environment.

We do not find such structures in plants

growing around us.

All such ways and means that organisms

adopt or develop over a certain period of

time in different conditions for better

survival are adaptations of organisms. We

may also say that adaptation is a feature that

is common in any population because it

provides some improvements for better

survival.

Activity-1:

Take a  Aloevera and a

Balsam plant in two separate pots. Water

each of them with two tablespoons of water.

Do not water them for a week. Observe

the condition of the plants after a week.

Which plant showed growth?

Which plant dried first? Why?

Activity-2:

Collect an aquatic plant out of a water

body( Eg. Duck weed, Hydrilla, Vallisneria

etc. either floating at the surface or

propping out of it). Carry it back home and

plant it in a pot and water it.

What do you observe? Compare

your observation with that of

activity1 and write a note on what

you find.

From the above activity we see that

some plants dry up without water very

quickly, while others can grow even with

very little water. Each of these plants are

adapted to the conditions in their

surroundings on the basis of need of water.

What is meant by adaptations?

Describe your opinion.

Organisms in nature create adaptable

situations around them on the basis of their

needs. They also adapt to situations

specifically. For example in Opuntia, the

leaves are reduced to spines so that

transpiration loss is checked and water is

stored in the tissues of the stem (succulent

stems). This helps the plant to live in

conditions of water scarcity as we come

across, in deserts. Aloe vera are found in

our surroundings these days as well but you

may have heard that they are generally called

as desert plants (xerophytes).

                Opuntia

                  Baobab

                 Cactus

Though these are called Living stones they are not stones. The

swollen leaves are adapted to desert conditions, minimizing water

loss and storingwater. These are also called Pebble Plants . Each pebble is actually a leaf with a cut window that lets in light. The stone like appearance deceives the animals and saves it from being eaten. Now a days, many Xerophytes aregrown as ornamental plants in pots at homes. Some plants as a whole seem to be flowers. Some with thorns, some have flowers with bright colour petals. Now a

days these kind of plants are used as gifts for Birthdays and other occasions also.

     

             Pebble plant

Adaptations in some more desert animals

The Side-Winder adder snake crawls

sideways with only a small amount of its

body pressed against the hot sand. This

technique helps it to keep itself cool. The

Golden Mole escapes the heat of the sun

by swimming through the sand just below

the surface. It rarely emerges out as it finds

all the needs below the ground

Some animals show extraordinary

ability to survive in the desert. The

Kangaroo Rat of western North American

desert can live without drinking water

through out its life. Because its body

synthesizes little water in the process of

digestion. The desert bird the Sand grouse

flies long distances to an oasis in search

of water, which it carries back in its crop

for its nestlings.

The furry soles of Fennec Fox helps it

walk on hot sand and loses heat through its

ears. When the sand becomes too hot the

sand diving lizard holds its feet in the air to

cool down.

            Rattle snake

              Sandgrouse

 

Adaptations in Aquatic ecosystems:

We shall study two different types of

ecosystems in water (aquatic ecosystems)

and some conditions in the environment that

influence adaptations.

Aquatic ecosystems are mainly

classified into two different types as Fresh

water and Marine ecosystems.

Ponds, Lakes, Rivers are the examples

of Fresh water Ecosystems

Seas, Oceans are the examples of

Marine Ecosystems

As the living conditions are different

we come across various adaptations in

several organisms living in these ecosystems.

General aquatic adaptation as can be

seen structurally (in body structure) are

like presence of some special air spaces

inside bodies or presence of such

substances that help organisms to swim and

float in water to inhabit different levels in

the water body, or bear specialized

structures to swim like flippers as in Turtles

and fins in fishes. Fishes, Dolphins etc have

floaters in their body (special structures of

their digestive canals) to be able to inhabit

particular levels in the water body.

Microscopic photosynthetic organisms

like planktons have droplets of oil in their

cells that keeps them float. Larger plants 

have long tough leaves and flexible stems.

Marine ecosystem:

Over the last 2,000 million years, plant

and animal life on earth has continuously

evolved from its simple beginnings in the

oceans to the complex existence on land

today. It is no accident that protoplasm, a

substance found in every living cell,

strongly resembles seawater. Although

some animals emerged from the sea

millions of years ago to fill all available

places on land, some remained in the ocean

and evolved and adapted to life beneath the

surface.

The ocean covers a larger part of the

planet, yet it remains a little understood

place as scientists have limited scope for

the study of habitats that lack physical

boundaries and a span of thousands of

miles.

Adaptations on the basis of light

penetration:

Euphotic zone

The organisms living in this zone are

mostly floaters and swimmers. Animals in

this zone usually have shiny bodies

reflecting light away to merge with shiny

water surface are transparent. These usually

have very sharp vision. Plants are mostly

green and photosynthetic activity is

maximum in this zone. Some flora and

fauna of this zone are trouts, herrings,

dolphins, jelly fishes, different type of coral

colonies which are extremely colourful,

different types of algae & sea grasses

(emergent plant species: rooted to the

sides, in marine ecosystems these are

rooted in the continental shelf area)

diatoms etc. Nearly 80% of marine flora

and fauna are found in this zone.

        Coral colonies

Bathyal zone:

Most of the plants found in this zone

are the red and brown kelps, sponges, corals

even animals with tubular bodies like

squids and large animals like whales etc.

Some of these have a flat body like the ray

fishes. They may have big eyes sensitive to

very dim light

                Ray fish

Abyssal zone:

These zones are

dark and cold

throughout the year.

Photosynthetic activity

is absent. Deep sea

animals are mostly

predators and

scavengers. The larger

forms have wide

mouths and huge curved teeth which prevent

escape of any prey. Absence of skeleton,

flattened bodies are some other

characteristics observed. Some also have

special structures that produce light on their

bellies, around their eyes(which are usually

nonfunctional that is, the organisms are

blind) and at the sides of their bodies, some

animals glow (shows bio luminiscence) in

the darkness of deep waters

              Angular fish

               Brittle Star

Freshwater Ecosystems:

Fresh water ecosystems are stagnant water types as well as running water types. They may vary in size from as small as a puddle and pond to a large lake, river etc. Just like the marine ecosystems, to

study environmental conditions in lakes, some zones are marked. The Littoral zone, Limnetic zone and Profundal zones on the

basis of light penetration. Based on availability of light different kinds of organisms are found in these zones. Different factors like light, salt content, food, oxygen affect the organisms and their

populations in different ways.

Littoral zone: The shallow zone near

the shore is also called as littoral zone. The

water near the shore is usually muddy or

turbid. This topmost and warmest zone at

the edge of a water body is home to Snails,

Clams, Insects, several Crustaceans, Fishes

and Amphibians and the eggs and larvae of

Dragonflies etc.

Several organisms in this zone have

well developed sight, usually have dull and

greyish bodies and are fast swimmers.

Plants like Mosses, Water lily, Vallisneria,

Hydrilla etc are found here along with

several types of algae. High photosynthetic

activity occurs in this zone. Predators of

this zone are Tortoise, Snakes and Ducks.

The limnetic zone is the open water

zone at the top of the water body and

consequently receives a good deal of light.

This zone contains a variety of freshwater

fish with bright shiny, greyish or silver

black scales that help them to merge with

the surroundings. Transparent or whitish

bodied crustaceans like Daphnia, Cyclops,

small Shrimps are also found in this zone.

There are different types of floating plants

like Water hyacinth, Wolffia, Pistia along

with a variety of algae. 

The profundal zone is dimly lit and

cold. Mostly heterotrophs (saprochytes -

microbes that decompose dead organisms)

are found in this region. Most of the

animals, the so called bottom dwellers, that

live here are mostly scavengers and

predators, for example Crustaceans, Crabs,

Fishes like Eels and Glossogobius (isika

dondu), Snails, Turtles etc. They adapt

themselves by feeding on dead animals that

settle down. Many kinds of bacteria

(detritus) thrive here that help in

decomposing the dead organisms. Mud of

the bottom floor, tiny particles of dead and

decaying matter of plants and animal bodies

make the water very turbid. Hence the

bottom dwellers , rely mostly on smell and

auditory (related to hearing) senses rather

than vision to aquire their food.

Adaptations in some aquatic plants

Partially submerged plants have

numerous air spaces inside the stems

,leaves ,roots that aid in gaseous exchange

and buoyancy. Leaf bases of Water Hyacinth

(Eichhornia crassipes) form air filled

structures to keep them afloat. In water

lilies leaves are flat, have an oily surface

with stomata present on the upper surface

of the leaf, while incompletely submerged

plants like Hydrilla, stomata are absent,

leaves are thin, stems are highly flexible.

The main adaptations that give Hydrilla an

advantage over other native plants are: it

can grow at low light intensities, it is better

at absorbing carbon dioxide from the water

(diffuses into leaves), it is able to store

nutrients for later use, it can tolerate a wide

range of water quality conditions for

example salinity(can grow in saline waters

as well), and it can propagate sexually and

asexually.

Other examples of adaptations

Adaptation to temperature in plants

The effect of temperature on plants of terrestrial ecosystem can be seen in different ways. Do all plants shed their leaves at

same time in a year throughout the world. Some plants in

temperate regions shed their leaves before the winter starts. This is to minimize transpiration loss as well as reduce photosynthetic and other metabolic activities, as low temperature renders several chemicals inactive for some time. In tropical regions some plants

shed their leaves before the start of summer. Plants growing in hot climates, usually keep the stomata closed during the day to reduce transpiration loss. High temperatures also lead to adaptations like reduced leaf. Let us recall why xerophytic plants have modified stems and leaves.

          Adaptive Radiation in Galapagos Finches

Try to guess if there is any relation between type of food taken and the structure of beak. The seed eaters had thick and heavy

beaks. The fruit eaters had stubby beaks. The insect eaters had sharp and long beaks. . Darwin observed that these birds had adapted to their immediate surrounding for food and shelter and showed a lot of

variation even within the same species, especially with respect to the form of beaks. He made a sketch of the same as shown in the above. Thus he concluded that adaptation was something that an organism is undergoing continuously, even within very closely related forms in a particularly geographically separated area.