Tuesday, December 13, 2011

zoo6: labeo rohita

zoo3: columbia

zoo3: calotes

z005: columbia notes

Thursday, June 23, 2011

bot-Physiology_krebs cycle

krebs cycle

The citric acid cycle — also known as the tricarboxylic acid cycle (TCA cycle), the Krebs cycle.It is a series of enzyme-catalysed chemical reactions, which is of central importance in all living cells, especially those that use oxygen as part of cellular respiration. In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion. The components and reactions of the citric acid cycle were established by discovery of Vitamin C.
In aerobic organisms, the citric acid cycle is part of a metabolic pathway involved in the chemical conversion ofcarbohydratesfats and proteins into carbon dioxide and water to generate a form of usable energy. Other relevant reactions in the pathway include those in glycolysis and pyruvate oxidation before the citric acid cycle, and oxidative phosphorylation after it. In addition, it provides precursors for many compounds including some amino acids and is therefore functional even in cells performing fermentation.



A simplified view of the process

  • The citric acid cycle begins with the transfer of a two-carbon acetyl group from acetyl-CoA to the four-carbon acceptor compound (oxaloacetate) to form a six-carbon compound (citrate).
  • The citrate then goes through a series of chemical transformations, losing two carboxyl groups as CO2. The carbons lost as CO2 originate from what was oxaloacetate, not directly from acetyl-CoA. The carbons donated by acetyl-CoA become part of the oxaloacetate carbon backbone after the first turn of the citric acid cycle. Loss of the acetyl-CoA-donated carbons as CO2 requires several turns of the citric acid cycle. However, because of the role of the citric acid cycle in anabolism, they may not be lost, since many TCA cycle intermediates are also used as precursors for the biosynthesis of other molecules.[6]
  • Most of the energy made available by the oxidative steps of the cycle is transferred as energy-rich electrons to NAD+, forming NADH. For each acetyl group that enters the citric acid cycle, three molecules of NADH are produced.
  • Electrons are also transferred to the electron acceptor Q, forming QH2.
  • At the end of each cycle, the four-carbon oxaloacetate has been regenerated, and the cycle continues.

Bot-ecology_biomes

Biomes



Biomes are defined as "the world's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment" (Campbell 1996). The importance of biomes cannot be overestimated. Biomes have changed and moved many times during the history of life on Earth. More recently, human activities have drastically altered these communities. Thus, conservation and preservation of biomes should be a major concern to all.

A biome is an area on the earth's surface that has a certain set of characteristics. There are seven kinds of biomes in the world: tundra, taiga, temperate forest, tropical rainforest, desert, grassland, and ocean. 



The Desert Biome


Deserts are places on earth that are characterized by little vegetation and rain. They are made up of sand or rocks and gravel. Deserts cover about one-fifth of all the land in the world. Most deserts lie along the Tropic of Cancer and Tropic of Capricorn, imaginary lines that lie north and south of the equator.
Oases are parts of the desert where plants grow and water is almost always available. An oasis is formed by a pool of water trapped between layers of rock beneath the desert floor. The regular water in an oasis allows people to settle in the desert and even grow crops.
Some deserts are named and nicknamed things like Death Valley, "the Empty Quarter," and "the Place from Where There is No Return" because of the lack of water there.
 The Taiga Biome


The taiga is the largest biome in the world. It covers large parts of Canada, Europe, and Asia. This forest is covered with coniferous trees. In fact, sometimes the taiga is called a coniferous forest.Conifer trees are often called evergreens. These trees have long, waxy needles instead of wide, flat leaves like hardwood trees. Evergreens do not loose their needles come wintertime. The needles stay on all year long.

The Grassland Biome

Grasslands are large areas with rolling hills of grasses and wildflowers. Grasslands are found on every continent but Antarctica. Sometimes grasslands are called prairies, savannahs, or steppes.
The roots of the grasses and small plants make the soil rich and great for farming. Some of the grasslands are used for animal grazing, too. The map below shows where grasslands are located around the world.




Temperate Forest Biome

Temperate forests are often called deciduous forests. In a temperate forest, most of the trees lose their leaves in the winter. During the fall, when the weather gets cooler, the trees begin to shut down. Their leaves turn beautiful shades of colors. Come winter time, the leaves fall off of the trees. Why do you think this is so?The deciduous trees must lose their leaves, because water is not available for the leaves to survive. Also, the trees are not strong enough to keep their leaves and hold up all the snow that comes in the winter.

                                          The Ocean Biome
Did you know that life on planet Earth began in the oceans more than 3 billion years ago?Over 70 percent of the earth's surface is covered by water. In fact, when seen from space, our earth looks blue, because of the large bodies of water which cover most of it. Although we speak of separate oceans, the world is really covered by one huge ocean in which the continents are islands!
There are four main oceans: the PACIFIC, ATLANTIC, INDIAN, and ARCTIC.
The Tundra Biome

The tundra is located around the North Pole in the Arctic Circle. For most of the year it is covered in snow. In the short summers, the snow and ice melt to leave pools of meltwater. The layer of earth beneath the tundra is frozen all year long. This is called the permafrost. Industrial activity in the tundra may add to the world's environmental problems. Dust and grime make the ice darker, so less heat is reflected from the ice and global warming is increased.
                                             The Rainforest Biome

The tropical rainforests of the world are located in the green areas on the map above. The tropical rainforest is the richest source of life on earth. It is a treasure chest of plant and animal life.
its good to include some basic information on above biomes:





         Biomes are the major regional groupings of plants and animals discernible at a global scale. Their distribution patterns are strongly correlated with regional climate patterns and identified according to the climax vegetation type. However, a biome is composed not only of the climax vegetation, but also of associated successional communities, persistent subclimax communities, fauna, and soils.
The biome concept embraces the idea of community, of interaction among vegetation, animal populations, and soil. A biome (also called a biotic area) may be defined as a major region of distinctive plant and animal groups well adapted to the physical environment of its distribution area.

Wednesday, June 22, 2011

bot-ecology_Xerophytes

Xerophytes (Adaptations to dry environment)

The plants which are growing in xeric (dry) environment (habitat) are called Xerophytes. Deserts are the best examples for xeric environment, where plant face inadequate water and excessive transpiration .xerophytes are classified into the following three categories-Ephemerals [the plants complete their life cycle within a short period. they also called “drought escapers” or “drought evaders”], Succulents [these plants have succulent, fleshy organs, to store to store high amount of water accumulated during rainy seasons. these xerophytes suffer dryness only in external environment],true xerophytes[these plants which are able to live under extreme dry conditions and high temperature].the xerophytes show the following adaptations.
Morphological adaptations
1. Stem shows stunted growth
2. Certain plants have under ground stem to tide over dry season.
3. Plants like acacia, zizyphus etc .have very hard ,woody stem with thick bark.
4. In many plants the leaves are reduced to scaly or spiny e.g.ruscus, asparagus etc.
5. Many plants have very small and narrow leaf blade to reduce the transpiration area.
6. Some plants have shining leaf surface to reflect light. E.g.nerium odorum.
7. In certain plant leaves leaves are very thick and leathery to reduce transpiration. E.g.calotropis procera
8. Many plants have waxy coating on the upper surface of leaves.
9. Folded type leaves are seen in some of the grasses to protect the
10. In non-succulent plants root system is several times larger than the aerial portion.
Anatomical adaptations
1. Presence of thick cuticle on the upper surface of leaves.
2. The epidermal cells are thick walled.
3. Multiple epidermal layers are seen on both upper and lower surface of leaves.
4. Stomata are reduced in numbers and are sunken type.
5. The stomata pits are filled with number of hairs.
6. Thick walled sclerenchyma cells are seen in the hypodermis. E.g. pinus needle
7. Few spongy parenchyma cells with small inter cellular spaces.
8. Presence of many layered palisade parenchyma
9. The cells are relatively smaller in size and vacuoles are small.
10. Well developed vascular tissues are present.

Tuesday, June 21, 2011

bot-ecology_Xerosere

Xerosere

Xerosere is a plant succession which is limited by water availability. It includes the different stages in a xerarch succession of ecological communities originated in extremely dry situation such as sand deserts, sand dunes, salt deserts; rock deserts etc. a xerosere may include lithoseres on rock and pasammoseres on sand.

Stages of Xerosere

Stage 1: Crustose Lichen stage


A bare rock consists of solid surface or very large boulders and there is no place for rooting plants to colonize. The crustose lichens like Licanora, Rhinodina can adhere to the surface of rock and absorb moisture from atmosphere. Therefore these colonize the bare surfaces of rocks fast. The Propagulis of these lichens are brought by air from the surrounding areas. These lichens produce acids which corrode the rock and their thalli collect wind blown soil particles among them that help in formation of a thin film of soil. When these lichens die their thalli decomposed to humus. This promotes soil building and the environment becomes suitable for growth of foliose and fruticose type of lichens.

Stage 2: Foliose and Fruitcose Lichen Stage

Foliose have leaf like thalli while the fruticose lichens are small bushes. They are attached by the substratum at one pint only. Therefore do not cover the soil completely. They can absorb and retain more water and are able to accumulate more dust particles. Their dead remains are decomposed to humus which mixes with soil particles and help building substratum and improving soil moisture contents further. The shallow depreciation in the rocks and crevices become filled with sold and top soil layers increases further. These autogenic changes favor growth and establishment of mosses. This community includes Permelia and Dermatpcarpom etc which have large leaf like thalli.

Stage 3: Moss Stage

The spores of xyrophytic mosses such as Tortula and Grimmia are brought to the rock whether they succeed lichens. They are rhizoids penetrates soil among the crevices secret acids and corrode the rocks. The bodies of mosses are rich in organic and inorganic compounds. When these die they add these compounds, to the soil to increase the fertility of the soil. Since mosses develop in patches they catch soil particles form air and help increasing substratum. The changing environment leads to migration of lichens and help invasion of herbaceous vegetation.

Stage 4: Herb Stage

Herbaceous weeds mostly annuals such as asters and evening primroses invade the rock. Their roots penetrate deep down, secret acids and enhance the process of weathering. Leaf litter and death herbs add humus to the soil. Shading of soil results in decrease in evaporation and there is a slight increase in temperature. As a result in decrease in evaporation and there is a slight increase in temperature. As a result the xeric condition begins to change and biennial and perennial herbs and xeric grasses begin to inhabit. This climatic conditions favor growth of bacterial and fungal populations resulting in increase in decomposition activity.

Stage 5: Shrub Stage:

Herb and grass mixture is invaded by scrub species such as Rhus and others. Early invasion of scrub is slow but once a few bushes have become established birds invade the area and help disperse scrub seeds. This results in dense scrub growth shading the soil and making conditions unfavorable for the growth of herbs which begin to migrate. Te soil formation continues and its moisture contents enhance. The environment becomes mesic or moderately moist.

Stage 6: Tree Stage

Change in environment favors colonization of tree species. The tree saplings begin to grow among the scrubs and establish themselves. The kind of tree species inhabiting the area depends upon the nature of the soil. In poorly drained soils oaks establish themselves. Te trees form canopy and shade the area. Shade loving shrubs continue to grow as secondary vegetation. Leaf litter and decaying roots weather the soil further and add humus to it making the habitat more favorable for growth to trees. Mosses and ferns make their appearance and fungi population grows abundantly.

Stage 7: Forest Stage or climax Stage

The succession culminates in a climax community, the forest. Many intermediate tree stages develop prior to establishment of a climax community. The forest type depends upon climatic conditions.