Ch. 14 Ecosystem & Energy Flow

 

Prof.Dr.Sadhana Nikam
Vice Principal
Rashtriya Jr. College, Chalisgaon
Biology Subject
Notes of XII Science
Ch.14 Ecosystems and Energy flow

Introduction :

Def : Ecosystem
*A self regulatory & self sustaining  structural and functional unit of biosphere is called an Ecosystem.
* Tansley (1935) coined the term  ecosystem.
* Types of Ecosystem:
*Natural  ecosystem : The ecosystems which operate under natural conditions without any  interference of man are called Natural  Ecosystems.
* Artificial ecosystems : The ecosystems which made and maintained artificially  by  man are called  Artificial ecosystems.

14.5 Ecological Succession :

Q.What is mean by Ecological Succession (1 Mks)
Def: The gradual & predictable change in the species composition of a given area is called Ecological succession.

Q. What is climax community (1 Mks)
Species diversity increase by sequential change in a definite order relating with time to form complex organisms is called Climax community.

Q. Enlist steps of Ecological  Succession (2 Marks)
The sequential steps of Ecological  Succession are
i. Nudation  ii. Invasion  iii. Ecesis  iv. Aggregation
v. Competition  & co-action  vi. Reaction  & Stabilization  

Q. What is mean by sera (1 Mark)
The entire sequence of  communities which successively change in a given area is called  Sera.

Q. What  is  mean  by  seral  stages (1 Mark)
The developmental  stages  of   ecological  succession  are  called
Seral  stages. 

Q. What are  Pioneers (1 Mark)
The  organisms  of  the  first  seral  stage  are  called  Pioneers.

Q. What  is  mean  by  Seral  communities (1 Mark)
The  individual  transitional  communities  are  called  as  Seral  communities.

Q. Enlist  types  of  Ecological  Succession (1 Mark)
There  are  two  types  of Ecological  Succession such  as 
i. Primary Succession  ii. Secondary  Succession.

Q. Write a  note  on Primary  Succession (2 Marks)

i. Def : The  Succession  which  start  in  the  area  where  living  organisms  not  occur  first  is  called  Primary  Succession.
ii. It  is  very  slow.
iii. Soil is require   to  form  biotic  community  in  a  primary  succession.
iv. Primary  Succession  require  several  hundred to  several  thousand years  to  produce  fertile  soil  on  bare rock.           v. Primary  Succession  occur  in  newly  cooled  lava, bare  rocks, newly  created  pond  etc.                                                             vi. Example : Primary  Succession  of  Aquatic  habitat.

Q. Write  a  note  on  Secondary  Succession (2 Marks)
i. Def : The Succession  which  start  in  an  area  where  living  organisms  once  existed  is  called  Secondary  Succession.
ii. It is  faster  than  primary  succession.
iii. Some  soil  or  sediment  is  essential  for  Secondary  Succession.
iv. Secondary  Succession  occur  in  areas  where  natural  biotic  communities  first  destroyed.
v. Secondary  Succession  occur  in  destroyed  farm lands, burned or  cut  forests, flooded  land etc.

Q. What  is mean by  Hydrarch  succession (1 Mark)
Def : The  succession  which  occur  in  the  area  where  water present in abundance  is  called Hydrarch  Succession.

Q. What is  mean  by  Xerarch Succession (1 Mark)
Def :The  succession which  occur  in  dry  area  is  called  Xerarch  Succession.

Q. Explain Hydrarch Succession of  Plants (2 Marks)
i. It is primary  succession  of  aquatic  habitat.
ii. The  pioneers  are  small  phytoplankton  followed  by  rooted
submerged  plants e.g. Hydrilla  &  rooted  floating  angiosperms
e.g. Lotus.
iii. These  followed  by  free  floating  plants e.g. Pistia & then reed  swamp e.g. Typha.
iv. These  followed  by  marsh  meadow  e.g. Cyperus  then  Shrub  e.g. Alnus &  finally  the  trees  e.g. Quercus.
v. Finally  the  climax  community  forest  form.
vi. After  passing  time  water  body  is  converted  into  land.
Refer  Text book  figure 14.13

Q. Explain  Xerarch  Succession  in  Plants (2 Marks)
i. The  desert  area  shows  xerarch  succession .
ii. It  begins  with  growth  of  crustose  lichens.
iii. These  lichens  produce  acid  to  dissolve  rocks which  after  weathering  of  rocks  form  soil.
iv.  Then  small  bryophytes  like  mosses  occur  followed  by  herbs, shrubs  and  then  trees.
v. At the  last  stage  a  stable  climax  forest  community  form.
Refer  Text  book  figure  14.12

Remaining  units  are not involved in syllabus of  2020-21.