Territorial behavior

 A territory is an area held and defended by an organism or group of organisms of the same or different species. Territorial behavior is common to all vertebrates except amphibian but is rare in non-vertebrates.

The exact function of territory formation varies from species to species, but in all cases, it ensures that each mating pair of organisms and their offsprings are adequately spaced to receive a share of the available resources, such as food and breeding space. In this way, species achieves optimum utilization of the habitat.

The size of territories occupied by any particular species varies from season to season according to the availability of environmental resources. Birds of prey and large carnivores have territories several square miles in area in order to provide all their food requirements. Herring gulls and penguins have territories of only a few square metres, since they move out of their territories to feed and use them for breeding purposes only.

Territories are found prior to breeding, usually by males. Defense of the area is greatest at the time of breeding and fiercest between males of the same species. There are a variety of behavioral activities associated with territory formation and they involve threat displays between owners of adjacent territories. These threat displays involve certain stimuli which act as releasers. E.g. An adult male robin would attack another adult male displaying a red breast and a bunch of red feathers, but not a young male robin which did not have a red breast. The level of aggression shown by an organism increases towards the centre of the territory. The aggressiveness of males is determined partly by the level of testosterone in the body and this can affect territory size. E.g. the territory size of a red

grouse can be increased by injecting the bird with testosterone. Territories are acquired through threats, gestures and postures in place of actual fighting. Having obtained a territory, many species especially carnivores proceed to mark out the boundary by leaving a scent trail. This may be done by urinating or rubbing parts of the body against objects called scent posts along the boundary of the territory.

Altruistic behavior

Altruism is a form of social behavior whereby one organism puts itself either at risk or personal disadvantage for the good of other members of the species. In the case of activities associated with and parental care, altruism is not so difficult to comprehend since the action is clearly in the interest of the parents, offsprings and species. E.g. the female baboon protects and cares for its offspring for almost six years whilst most bird species feed and protect their demanding offprings until they are capable of fending for themselves. What is not so clear is the reason why some organisms give support to organisms which are not their offspring E.g birds and monkeys call out warnings to others in danger and female monkeys carry and care for the babies of other monkeys. In insects such as honey bees, wasps and ants, sterile female workers are prevented from producing offsprings, yet they spend their lives looking after their brothers and sisters. Hence, helping their sister (queen) to reproduce, they are effectively aiding in the production of queens, workers an drones with a genetic complement closer to their own than if they had offspring of their own. The conferring of a genetic advantage on closely related organisms forms the basis of altruistic behavior.

Altruistic behavior is very common amongst primates and varies from the extremes of social protection which exist between members of the same troop (monkeys), through acts of mutual grooming and food sharing (apes) to deliberate acts of self-sacrifice for family (God for humans). The extent of altruistic behavior appears to be related to close relatives (kin) such as offspring and siblings (brothers, sisters cousins) with whom they share certain alleles. Thus the adaptive significance of altruistic behavior is to increase the frequency of those alleles common both to the donor and recipient(s) of the altruistic behavior

Pathogenic Properties of Virus

• Viruses have mechanisms to evade host defenses viruses grow inside host cells to hide from immune defense.

• Kill immune cells e.g. HIV – TH Cells.

• Cytopathic effects: - The visible effects of viral infection on host cell. Some effects will kill the cell and some will just change the cells.

• Viruses stop DNA, RNA and/or protein synthesis e.g. Herpes virus block mitosis.

• LySOSomal autolysis of host cells e.g. Influenza: bronchiolar epithelium.

• Production of inclusion bodies (visible viral parts inside the cell) can identify a particular virus e.g. Rabies virus: Negri bodies.

•  Syncytium formation (neighboring cells fuse together) e.g. Varicella Zoster virus.

• Change in cell function e.g. Measles, production of interferons by host cell (triggers host immune response), induce antigenic changes on host cell surface (triggers destruction of infected cell by host immune response).

• Induce chromosomal changes, cell transformation: may activate or deliver oncogenes resulting in loss of contact inhibition (cancer) e.g. Papilloma virus.

Theories on membrane structures

• In 1902 it was thought that the membranes had only lipids (Overton). 
• In 1926 Gorter and Grendell proposed that lipids are capable of forming a double layer.
• In 1935 Danielli and Davson proposed the lipid bilayer model that includes proteins adhering to both lipid-aqueous interfaces.
• Artificial model systems such as the liposomes supported the idea of Danielli and Devson.
• A droplet of lipid made soluble in an organic solvent can be spread over a small hole on a septum that divides two chambers containing water.
• This set up is useful to study biophysical properties of a bilayer such as permeability and electrical resistance.
• Channels for ions can be formed by adding certain proteins or polypeptides.
• Liposomes act as excellent carriers for different molecules such as chemotherapeutic compounds, insulin and antibodies.

Fluid mosaic model

• Fluid mosaic model proposed by S.J. Singer and G.L. Nicolson (1972) was finally acceptable to most biologists.
• This model recognizes that lipids and proteins are in a mosaic arrangement.
• It also recognizes that there is translational movement of lipids and proteins within the lipid bilayer.
• Non covalent interactions ensure a fluid like state for the membranes.
• Integral proteins are intercalated into the continuous lipid bilayer.
• Polar/hydrophilic regions of proteins protrude from the surface while the nonpolar/hydrophobic regions are embedded inside.

Unit membrane model 

• Robertson in 1959 postulated the unit membrane model.
• This model stated that the central layer of plasma membranes is made up of hydrocarbon chains of lipids and the proteins constitute the dense surrounding layers on both sides when viewed through an electronmicroscope.
• Unit membrane model turned out to be an over simplification model as it can’t account for the number of protein molecules present across the membranes. 

Entomophily

• The pollination which takes place with the help of insects is known as entomophily. Most of insect pollination (80%) occurs only by honey bees.
• Favourable colour of honey bees is yellow, but they are blind to red colour.
• Majority of insect pollinated flowers are large, colourful, fragrant and rich in nectar, when the flowers are small, a number of flowers are clustered into an inflorescence to make them conspicuous.
• Night blooming plants are pollinated by moths. They are highly scented. Their flowers are generally white coloured.
• The flowers pollinated by flies and beetles secrete foul odour to attract these animals.
• The pollen grains of insect pollinated flowers become sticky due to presence of pollen kit.
• Most of entomophilous plants are ornamental plants. Ornamental plants utilize their maximum energy in this pollination and develop different types of adaptation for attraction of insects. Their flowers are attractive. Animals are attracted to flowers by colour and/or fragrance. e.g. Cucumber, Mango, Peepal, Coriander, Papaya, Onion, Lobia, Cotton, Tobacco, Rose, Lemon, Eucalyptus, Banana.
• Some of the following plants have developed special adaptation, for insect pollination.
• Yucca plant develops symbiotic relationship with a species of moth, Pronuba yuccasela moth (Tegeticula moth). The pollination in "Yucca takes place only by Pronuba female moth. This insect lays eggs in the locule of the ovary of flower. The larvae of moth come out of the eggs as the seeds start developing. Life cycle of both depends on each other. Moth and the Yucca plant can not complete their life cycles without each other.
• In tallest flower of Amorphophallus (the flower itself is about 6 feet in height), process of pollination is same as Yucca means it provides space (safe place) for laying eggs.Floral rewards : To sustain animals visits, the flowers have to provide rewards to the animals. Nectar and pollen grains are usual floral rewards. In some species floral rewards are in providing safe places to lay eggs. e.g. Yucca, Amorphophallus.
• Pollen / Nectar robbers : Many insects may consume pollen or the nectar without bringing about pollination, such floral visitors are referred to as pollen / nectar robbers.
• Orchid Ophrys flower is pollinated by wasp [Colpa aurea] by means of pseudo copulation. The appearance and odour of the flower is like female wasp [Mimicry].
• Nymphaea (water lily), water hyacinth, Nelumbo or Nelumbium (lotus), Alisma are also entomophilous plants while they are hydrophytes.
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Anemophily

• When the pollen grains are transferred from one flower to the another flower through the wind then it is called anemophily and flower is known as anemophilous flower.
• The anemophilous plants produce enormous amount of pollen grains.
• The pollen grains are very small, lightweight and dry (non-sticky).
• Stigma is large often hairy or feathery to easily trap air borne pollen grains and mucilaginous (Sticky).
• They often possess well exposed stamens so that the pollens are easily dispersed into wind currents.
• Yellow clouds of pollens are formed by Pinus tree due to the pollen grains which is called "sulphur Shower".
• Winged pollen grains are found in Pinus.
• Anemophilous flowers are neither attractive nor with fragrance. They do not have nectar glands. Anemophilous flowers are generally unisexual.
• Maximum loss of pollen grains takes place in this type of pollination. It is completely non-directional process.
• Wind pollinated flowers often have a single ovule in each ovary and numerous flowers are packed into an inflorescence e.g. corn cob. The tassels is styles and stigmas which wave in the wind to trap pollen grains.
• Pollination by wind is more common amongst abiotic pollinations.
• Wind pollination is quite common in grasses. e.g. - Gymnosperms, maize (corn), sugarcane, bamboo, coconut, Cannabis, grasses, date palms, papaya. 
  
  
  

Incomplete dominance

 Works on problems of heredity have shown that the dominance is not of universal occurrence and there are many examples of incomplete dominance in which the genes of an allelomorphic pair express themselves partially when present together in the hybrid. As a result the heterozygotes (Aa) are phenotypically intermediate between two homozygous types (AA* aa).

For instance, when red snapdragon plants are crossed with white snapdragon plants, all the F₁ hy­brids have pink flowers. This third phenotype results from the heterozygote flowers having less red pigment than the red homozygotes. The breeding of the F₁ hybrids produces F₂ offspring with a phenotypic ratio of 1 red to 2 pink to 1 white. In incomplete dominance we can distinguish the heterozygotes from the two homo­zygous varieties, and the genotypic and phenotypic ratios for the F₂ generation are the same, 1:2:1. The segregation of the red and white alleles in the gametes produced by the pink-flowered plants confirms that the genes for flower color are heritable factors that maintain their identify in the hybrids; that is, inheritance is particulate.

It is incomplete dominance - the kind of inheritance of allelic genes where a cross between organ­isms with two different phenotypes (AA x aa) produces offspring with a third phenotype that is a blending (Aa) of the parental traits. Incomplete dominance is manifested when the interacting enzymes are slightly different in their activity.

In humans, traits with incomplete dominant inheritance are size of nose, salience of lips, size of mouth and eyes, distance between eyes, hair types (straight, wavy) and such hereditary disorders as Friedreich’s ataxia, cystinuria are inherited according to principle of incomplete dominance. For any character, the domi- nant/recessive relationship we observe depends on the level at which we examine phenotype; e.g., con­sider a fatal recessive Tay-Sachs disease, inherited disorder of lipid metabolism when crucial enzyme hexosaminidase does not work properly. Brain cells of Tay-Sachs babies lack a crucial lipid-metabolizing enzyme. Thus, lipids accumulate in the brain, causing the disease symptoms and ultimately leading to death.

At the organism level of normal versus Tay-Sachs phenotype, the Tay-Sachs allele qualifies as a re­cessive (aa).

At the biochemical level,however, we observe intermediate phenotype characteristic of incomplete dominance. The hexosaminidase enzyme deficiency can be detected in heterozygotes who have an activity level of the lipid-metabolizing enzyme that is intermediate between individuals homozygous for the normal allele and individuals with Tay-Sachs disease. Heterozygous individuals are genetically programmed to produce only 40-60% of the normal amount of an enzyme that prevents the disease.