👉Health:
- state of complete physical, mental and social well-being
- increases productivity
- economic prosperity.
- increases longevity of people
- reduces infant and maternal
- mortality.
👉It is estimated that more then 70 per cent of the world
livestock population is in India and China.
contribution to the world farm produce is only
25 per cent, i.e., the productivity per unit is very low.
👉Inbreeding
- purelines
- Inbreeding increases homozygosity
- Inbreeding exposes harmful recessive genes that are eliminated by selection.
- accumulation of superior genes
- increases the productivity
👉Inbreeding depression
- continued inbreeding, especially close inbreeding, usually reduces fertility and even productivity. This is called inbreeding depression
- If mated with unrelated superior animals of the same breed. This usually helps restore fertility and yield.
👉Out-crossing:
- mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4-6 generations.
- breeding method for animals that are below average in productivity in milk production, growth rate in beef cattle, etc.
- A single outcross often helps to overcome inbreeding depression.
👉Water:
- life on earth originated in water and is unsustainable without water.
- The productivity and distribution of plants is also heavily dependent on water
- The salt concentration (measured as salinity in parts per thousand),
- is less than 5 in inland waters,
- 30-35 in the sea
- and > 100 in some hypersaline lagoons.
- tolerant of a wide range of salinities (euryhaline)
- narrow range (stenohaline)
👉The components of the ecosystem are seen to function as a unit when
you consider the following aspects:
(i) Productivity;
(ii) Decomposition;
(iii) Energy flow; and
(iv) Nutrient cycling.
👉A constant input of solar energy is the basic requirement for any ecosystem
👉Primary production is defined as the amount of
biomass or organic matter produced per unit area over a time period by
plants during photosynthesis. It is expressed in terms of weight (gm^–2) or
energy (kcal m^–2).
👉The rate of biomass production is called productivity.
It is expressed in terms of gm^–2 yr^–1 or (kcal m^–2) yr^–1
👉Productivity can be divided into gross primary
productivity (GPP) and net primary productivity (NPP).
👉Gross primary
productivity of an ecosystem is the rate of production of organic matter
during photosynthesis.
👉A considerable amount of GPP is utilised by plants
in respiration. Gross primary productivity minus respiration losses (R),
is the net primary productivity (NPP).
👉Net primary productivity is the available biomass for the consumption
to heterotrophs (herbiviores and decomposers)
👉Secondary productivity
is defined as the rate of formation of new organic matter by
consumers.
👉Primary productivity depends on the plant species inhabiting a
particular area. It also depends on a variety of environmental factors,
availability of nutrients and photosynthetic capacity of plants.
👉The annual net primary
productivity of the whole biosphere is approximately 170 billion tons
(dry weight) of organic matter.
👉Of this, despite occupying about 70 per
cent of the surface, the productivity of the oceans are only 55 billion tons.
👉Productivity, decomposition, energy flow, and nutrient cycling are
the four important components of an ecosystem.
👉Decomposition involves three processes, namely fragmentation of
detritus, leaching and catabolism
👉Energy flow is unidirectional.
👉Nutrient cycling is of two types—gaseous
and sedimentary (phosphorus)..
👉Succession begins with invasion of a bare lifeless
area by pioneers which later pave way for successors and ultimately a
stable climax community is formed. The climax community remains
stable as long as the environment remains unchanged.
👉In aquatic ecosystems, the limiting factor for the productivity
is_________.
Answer: light
👉There
is more solar energy available in the tropics, which contributes to
higher productivity; this in turn might contribute indirectly to greater
diversity.
👉The largely tropical Amazonian rain forest in South
America has the greatest biodiversity on earth- it is home to more
than 40,000 species of plants, 3,000 of fishes, 1,300 of birds, 427
of mammals, 427 of amphibians, 378 of reptiles and of more than
1,25,000 invertebrates.
👉Colombia located near the equator has nearly 1,400 species of birds
while New York at 41° N has 105 species and Greenland at 71° N
only 56 species. India, with much of its land area in the tropical
latitudes, has more than 1,200 species of birds.
👉Ecologists have discovered that the
value of Z lies in the range of 0.1 to 0.2 generally.
Z = slope of the line (regression
coefficient)
👉A stable community should not show too much variation
in productivity from year to year; it must be either resistant or resilient to
occasional disturbances (natural or man-made), and it must also be
resistant to invasions by alien species.
👉David Tilman’s
long-term ecosystem experiments using outdoor plots provide some
tentative answers. Tilman found that plots with more species showed
less year-to-year variation in total biomass. He also showed that in his
experiments, increased diversity contributed to higher productivity.
👉In general, loss of biodiversity in a region may lead to (a) decline in
plant production, (b) lowered resistance to environmental perturbations
such as drought and (c) increased variability in certain ecosystem processes
such as plant productivity, water use, and pest and disease cycles.
👉Presently, 12 per cent of
all bird species, 23 per cent of all mammal species, 32 per cent of all
amphibian species and 31per cent of all gymnosperm species in the world
face the threat of extinction.
👉more than 15,500 species
world-wide are facing the threat of extinction.
👉rain forests now cover no more than 6 per cent.
👉Species extinctions
in the last 500 years (Steller’s sea cow, passenger pigeon) were due
to overexploitation by humans.
👉Alien species invasions:
The Nile perch introduced into Lake Victoria in east Africa led
eventually to the extinction of an ecologically unique assemblage of
more than 200 species of cichlid fish in the lake.
carrot grass
(Parthenium), Lantana and water hyacinth (Eicchornia).
African catfish Clarias gariepinus for
aquaculture purposes is posing a threat to the indigenous catfishes
in our rivers.
👉Important explanations for the species richness of
the tropics are: Tropics had more evolutionary time; they provide a
relatively constant environment and, they receive more solar energy
which contributes to greater productivity.
👉34
‘biodiversity hotspots’ in the world have been proposed for intensive
conservation efforts. Of these, three (Western Ghats-Sri Lanka,
Himalaya and Indo-Burma) cover India’s rich biodiversity regions.
👉Our
country’s in situ conservation efforts are reflected in its 14 biosphere
reserves, 90 national parks, > 450 wildlife sanctuaries and many sacred
groves.
👉Nearly 700 species have become extinct
in recent times
👉Plants that are adapted to dry tropical regions have the C4 pathway
👉C4 plants are special: special type of leaf anatomy,
tolerate higher temperatures, response to high light intensities,
lack a process called photorespiration and have greater productivity
👉The fact that C3 plants respond to higher CO2 concentration by
showing increased rates of photosynthesis leading to higher productivity
has been used for some greenhouse crops such as tomatoes and bell
pepper. They are allowed to grow in carbon dioxide enriched atmosphere
that leads to higher yields.
👉C4 plants show
saturation at about 360 μlL-1 while C3 responds to increased CO2
concentration and saturation is seen only beyond 450 μlL-1. Thus, current
availability of CO2 levels is limiting to the C3 plants.
👉Cultivation of hybrids has tremendously increased
productivity. One of the problems of hybrids is that hybrid seeds have
to be produced every year.
👉Because of the importance of apomixis in hybrid seed industry,
active research is going on
