ORGANISMS AND POPULATIONS

ORGANISMS AND POPULATIONS

 

ORGANISM AND ITS ENVIRONMENT:

·         Rotation of sun and the tilt of its axis cause annual variations in the intensity and duration of temperature, resulting distinct seasons.

·         These variations along with annual variations in precipitation, forms major biomes, such as desert, rain forest, and tundra.

·         Temperature, water, light and soil are the key elements that lead to so much variation in the physical and chemical conditions of habitats.

·         Both abiotic (physic-chemical) and biotic components (pathogen, parasites, predators, competitions) characterize the habitat of an organism.

Major abiotic factors:

Temperature:

·         Temperature decreases progressively from equator towards the pole and high altitudes to > 50^o C in tropical deserts in summer.

·         Thermal springs and deep-sea hydrothermal vents are unique with >100^o C.

·         Temperature affects the kinetics of enzymes, BMR and other physiological actions.

·         Eurythermals: organism which can tolerate wide range of temperatures.

·         Stenothermal: organism which can tolerate narrow range of temperatures.

 

Water:

·         Water is also important factor that influence the life of organism.

·         The productivity and distribution of plants is also depends on water.

·         The salinity varies in aquatic environment:

o    5% in inland waters (fresh water)

o    30-35 in sea water

o    More than 100percent in hyper saline lagoons.

 

·         Euryhaline: organism which can tolerate wide range of salinity

·         Stenohaline: organism which can tolerate narrow range of salinity.

Light:

·         Plant produce food by photosynthesis, which only possible in presence of light. Hence it very important for autotrophs.

·         Plant species (herbs and shrubs) adapted for photosynthesize under canopy

·         Sunlight is required for photoperiodic response like flowering.

·         Animals use diurnal and seasonal variations in light intensity and photoperiod as cues for timing their foraging, reproductive and migration.

Soil:

·         Properties of soil vary according to the climate, the weathering process.

·         Soil composition, grain size and aggregation determine the percolation and water holding capacity of the soil.

·         These characteristic along with pH, mineral composition and topography determine to a large extent the vegetation in any area.

·         The sediment-characteristic often determine the type of benthic animal in aquatic environment.

Response to Abiotic Factors:

·         Homeostasis; the process by which the organism maintain a constant internal environment in respect to changing external environment.

How does organism cope with the changing environment?

Regulate:

·         Some organisms are able to maintain homeostasis physiological (sometimes behavioral also) means which ensures constant body temperature, constant osmotic concentration.

·         All birds and mammals and few lower invertebrates are capable of such regulation i.e. thermoregulation and osmoregulation.

·         Success of mammals is due to thermoregulation.

·         We maintain a constant body temperature of 37^oC.

·         When outside temperature is high we sweat profusely and evaporative cooling take place to bring body temperature down.

·         In winter due to low temperature outside our body temperature falls below 37^oC, we start to shiver, to generate heat to raise body temperature.

Conform: (i) Majority (99%) of animals and plants cannot maintain a constant internal environment; their body temperature varies according to ambient temperature.

·         In aquatic animals the osmotic concentration of body fluid varies with ambient water osmotic concentration.

·         All the above animals and plants are simply called as conformer.

Why the conformer not evolved to became regulators?

·         Thermoregulation is energetically expensive for many animals.

·         Small animal like shrews and humming birds cannot afford so much energy for thermoregulation.

·         Heat loss or heat gain is a function of surface area.

·         Small animals have larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside; then has to expend much energy to generate body heat through metabolism.

·         This is why very small animals are rarely found in Polar Regions.

Alternative response for stressful conditions is localized or remains for short duration.

 

Migrate:

• The organism moved away temporarily from the stressful habitat to a more hospitable area and return when stressful condition is over.
• Bird migrate form the colder region to warmer region.

Suspend:

• Thick walled spores are formed in microbes to overcome unfavourable stressful external environment. Spores germinate in favourable condition.
• In higher plants seeds and other vegetative reproductive structures are means to tide over the stress. They reduce their metabolic activity and going into a state of ‘dormancy’.
• Hibernation: during winter animals like bears escape in time
• Aestivation: animals like snail and fish avoid summer related problem like heat and desiccation.
• Diapauses: many zooplanktons undergo a stage of suspended development in unfavourable conditions.

ADAPTATION:

• Adaptation: is any attribute of the organism (morphological, physiological, and behavioral) that enables the organism to survive and reproduce in its habitat.

Adaptation of animal in desert:

• Kangaroo rat meets their water requirement from oxidation of fat.
• Excrete very concentrate urine to conserve water.

Adaptation of plant in desert (xerophytes)

• Thick cuticle on their leaf surfaces.
• Sunken stomata, both to reduce transpiration.
• Have special photosynthetic pathway (CAM), stomata closed during day time and remained open during night.
• Opuntia has no leaf- they are reduced to spines.
• Photosynthesis takes place in flat green stems.

Adaptation of animal in cold climate:

• Allen’s Rule: mammals from colder climates generally have shorter ears and limbs to minimize heat loss.
• Seals of polar aquatic seas have a thick layer of fat called blubber below their skin that acts as insulator and reduces loss of body heat.

Adaptation in high altitude:

• A person move to high altitude (>3,500 meter), develop altitude sickness.
• Symptoms developed are nausea, fatigue and heart palpitations.
• This is due to low atmospheric pressure of high altitudes; the body does not get enough oxygen.

How the bodies solve the problem?

• The body compensates low oxygen availability by increasing red blood cell production.
• The body compensates decreasing binding capacity of hemoglobin with oxygen by increasing rate of breathing.

Behavioral adaptation:

• Desert lizards are conformer hence they cope with the stressful environment by behavioral adaptations:
• They bask in the sun and absorb heat when their body temperature drops below the comfort zone in winter.
• Move to shade when the ambient temperature starts increasing.
• Some species burrowing into the soil to hide and escape from the above-ground heat.

POPULATION:

Population attributes:

• Population: a group of individual living in a well defined geographical area, share or compete for similar resources, potentially interbreed.
• Birth rate and death rate refers to per capita births and deaths respectively.
• Another attribute is sex ratio. The ratio between male female in a population.
• If the age distribution is plotted for a population the resulting structure is called age pyramid.
• The shape of the pyramids reflects the growth status of the population like growing, stable or declining.
• The population size is more technically called as population density.

Methods for measurement of population density:

·         Counting the number

·         Percent cover

·         Biomass.

·         Pug marks and fecal pellets for tiger census

Population growth:

• The size of the population changes depending on food availability, predation pressure and reduce weather.
• Population size fluctuated due to changes in four basic processes, two of which (Natality and immigration) contribute an increase in population density and two (mortality and emigration) to a decrease.
• Natality: number of birth in given period in the population.
• Mortality: number of deaths in the population in a given period of time.
• Immigration: is the number of individuals of same species that have come into the habitat from elsewhere during a given period of time.
• Emigration: number of individuals of the population who left the habitat and gone elsewhere during a given time period.
•   If  ‘N’  is  the  population  density  at  time  ‘t’,  then  its  density  at  time  t  +  1  is  :

Where B = the number of births
I = the number of immigrants
D = the number of deaths
E = the number of Emigrants.
N = Population Density
r = Intrinsic rate of natural increase
t = Time period
K  =  Carrying  capacity  (The  maximum  population  size  that  an  environment  can  sustain)

Exponential growth:

• The Exponential growth equation is  N_t = N₀e^rt
• Nt  =  Population  density  after  time  t
• N0  =  Population  density  at  time  zero
• r  =  intrinsic  rate  of  natural  increase
• e  =  the  base  of  natural  logarithms  (2.71828)

Exponential growth (‘J’ shape curve is obtained).
*    When resources are not limiting the growth.
*   Any  species  growth  exponentially  under  unlimited  resources  conditions  can  reach enormous  population  densities  in  a  short  time.
*    Growth is not so realistic.
Logistic growth model

• Verhulst-Pearl  Logistic  Growth  is  described  by  the  following  equations 
• dN/dt  =  rN  (K–N  /  N)
• Where  N  =  Population  density  at  time  t
• r  =  Intrinsic  rate  of  natural  increase
• K  =  Carrying  capacity

Logistic Growth (Sigmoid curve is obtained)

• When responses are limiting the Growth.
• Resources  for  growth  for  most  animal  populations  are  finite  and  become  limiting.
• The logistic growth model is a more realistic one.

POPULATION INTERACTIONS:

Predation:

• Organism of higher trophic level (predator) feeds on organism of lower trophic level (prey) is called the predation.
• Even the herbivores are not very different from predator.
• Predator acts as a passage for transfer of energy across trophic level.
• Predators keep prey populations under control.
• Exotic species have no natural predator hence they grow very rapidly. (prickly pear cactus introduced in Australia created problem)
• Predators also help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species. (Pisaster starfish field experiment)

Defense developed by prey against predators:

Animals:

• Insects and frogs are cryptically coloured (camouflaged) to avoid being detected by the predator.
• Some are poisonous and therefore avoided by the predators.
• Monarch butterfly is highly distasteful to its predator (bird) due to presence of special chemical it its body. The chemical acquired by feeding a poisonous weed during caterpillar stage.

Plants:

• Thorns in Acacia, Cactus are morphological means of defense.
• Many plants produce and store some chemical which make the herbivore sick if eaten, inhibit feeding, digestion disrupt reproduction, even kill the predators.
• Calotropis produces poisonous cardiac glycosides against herbivores.
•  Nicotine, caffeine, quinine, strychnine, opium etc. are produced by plant actually as defenses against the grazers and browsers.

 

Competition:

• Interspecific competition is a potent force in organic evolution.
• Competition generally occurs when closely related species compete for the same resources that are limiting, but this not entirely true:
• Firstly: totally unrelated species could also compete for the same resources.
• American lakes visiting flamingoes and resident fishes have their common food, zooplanktons.

 

• Secondly: resources need not be limiting for competition to occur.
• Abingdon tortoise in Galapagos Islands became extinct within a decade after goats were introduced on the island, due to greater browsing ability.

 

• Competitive release: A species, whose distribution is restricted to a small geographical area because of the presence of a competitively superior species, is found to expand its distributional range dramatically when the competing species is experimentally removed.
• Connell’s elegant field experiment showed that superior barnacle Balanus dominates the intertidal area and excludes the smaller barnacle Chathamalus from that zone.

 

• Gause’s ‘competitive Exclusion Principle’: two closely related species competing for the same resources cannot co-exist indefinitely and the competitively inferior will be eliminated eventually.
• Resource partitioning: If two species compete for the same resource, they could avoid competition by choosing, for instance, different times for feeding or different foraging pattern.
• MacArthur showed five closely related species of warblers living on the same tree were able to avoid competition and co-exist due to behavioral differences in their foraging activities.

Parasitism:

• Parasitic mode of life ensures free lodging and meals.
• Some parasites are host-specific (one parasite has a single host) in such a way that both host and parasite tend to co-evolve.

Parasitic adaptation

• Loss of unnecessary sense organs.
• Presence of adhesive organs or suckers to cling on to the host.
• Loss of digestive system.
• High reproductive capacity
• Parasites having one or more intermediate host or vectors to facilitate parasitisation of its primary host.
• Liver fluke has two intermediate hosts (snail and a fish) to complete its live cycle.

 Effects on the host:

• Parasite always harms the host.
• They reduce the survival, growth and reproduction of the host.
• Reduce its population density.
• They make the host more vulnerable to the predators, by making it physically weak.

 

•  Ectoparasite: feeds on the external surface of the host.
• Lice on human
• Ticks on dog
• Marine fish infested with copepods
• Cuscutaa parasitic plant grow on hedge plants.

 

• Endoparasites: are those that live inside the host body at different sites.
• Life cycle is more complex.
• Morphological and anatomical features are greatly simplified.
• Highly developed reproductive system.

 

• Brood parasitism:
• Special type of parasitism found in birds.
• The parasitic birds lay its eggs in the nest of its host and let the host incubate them.
• The egg of the host is very similar with the egg of the host.
• Cuckoo lays eggs in the nest of the crow.

Commensalism: This is the interaction in which one species benefits and the other is neither benefited nor harmed.

• Orchids growing as an epiphyte on a mango branch.
• Clown fish living among tentacles of sea anemone.
• Barnacles on back of whales.
• Cattle Egret and grazing cattle.

Mutualism: interaction between two living organism, both are equally benefited, no one is harmed.

• Lichen: a mycobiont and a Phycobiont.
• Mycorrhiza: relationship between fungi and root of higher plant.
• Pollinating insects and flowering plants.
• Fig trees and its pollinating agent wasp.

Sexual deceit

• Mediterranean orchid Ophrys employs ‘sexual deceit’.
• Petal of the flower resembles the female bee.
• The male bee attracted to what it perceives as a female, ‘pseudocopulates’ with the flower but does not get any benefits.

 

 

 

 

 

 

 

 

BIOTECHNOLOGY AND ITS APPLICATIONS

BIOTECHNOLOGY AND ITS APPLICATIONS

 

The critical areas of biotechnology are:

·         Providing the best catalyst in the form of improved organism usually a microbe or pure enzyme.

·         Creating optimal condition through engineering for a catalyst to act.

·         Downstream processing technologies to purify the protein/organic compound.

BIOTECHNOLOGICAL APPLICATIONS IN AGRICULTURE:

·         Plants, bacteria, fungi and animals whose genes have been altered by manipulation are called Genetically Modified Organisms (GMO).

 

·         Advantages of Genetic Modification in plants.

o    Made crops more tolerant to abiotic stresses (cold, drought, salt, heat)

o    Reduce reliance on chemical pesticides (pest resistant crop)

o    Helped to reduce post harvest losses.

o    Increased efficiency of mineral usage by plants.

o    Enhanced nutritional values of food e.g. vitamin A enriched rice.

Bt Cotton:

·         Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).

·         B.thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein.

·         These proteins are present in inactive protoxin form, but become active toxin in the alkaline pH of insect gut.

·         The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of insect

·         Specific Bt toxin genes were isolated form B. thuringiensis and genetically transferred to several plants such as cotton.

·         Crystal proteins are produced by a gene called cry in B. thuringiensis.

·         The protein coded by genes cryIAc and cryIIAb control the cotton bollworms.

·         The protein coded by gene cryIAb controls corn borer.

Pest resistant plants:

·         Several nematodes parasitize a wide variety of plants and animals including human beings.

·         A nematode Meloidegyne incognitia infects the root of tobacco plants and causes a great reduction in yield.

·         Strategy based on RNA interference (RNAi) prevents this infestation.

·         Process by which double-stranded RNA (dsRNA) directs sequence-specific degradation of mRNA

Steps of RNA interference:

·         Double stranded RNA is produced endogenously or exogenously.

·         Using Agrobacterium vectors nematode specific genes were introduced into the host plant (tobacco plant).

·         Introduction of DNA produces both sense and antisense RNA in the host.

·          These two RNA’s being complementary to each other formed a double stranded (dsRNA) that initiated RNAi.

·         The dsRNA injected into the host plant from outside called exogenous dsRNA.

·         The dsRNAs are cleaved into 21-23 nt segments (“small interfering RNAs”, or siRNAs) by an enzyme called Dicer.

·         siRNAs are incorporated into RNA-induced silencing complex (RISC) 

·         Guided by base complementarity of the siRNA, the RISC targets mRNA for degradation.

·         The consequence was that the parasite could not survive in a transgenic host.

BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE:

·         Biotechnology enables mass production of safe and more effective therapeutic drugs.

·         Recombinant therapeutics does not induce unwanted immunological responses as is common in case of similar products isolated from non-human sources.

·         At present around 30 recombinant therapeutics, approved for human-use.

Genetically Engineered Insulin:

·         Taking insulin at regular interval of time is required for adult-onset diabetes.

·         Previously the source of insulin was the slaughtered cattle and pigs.

·         This insulin caused allergy in some patients.

·         Each insulin made of two short polypeptide chains; chain A and chain B that are linked together by disulphide linkage.

·         Insulin synthesized in pancreas as pro-hormone which is a single polypeptide with an extra stretch called C-peptide.

·         C-peptide is removed during matured insulin.

·         In 1983 Eli Lilly an American company prepared two DNA sequences corresponding to A and B, chains of human insulin and introduced them in plasmids of E.coli to produce insulin chains.

·         Chain A and chain B produced separately, extracted and combined by creating disulfide bonds to form mature human insulin.

 

Gene therapy:

• Gene therapy is an attempt to cure hereditary or genetic diseases.
• Genes are inserted into a person’s cells and tissue to treat the disease.
• The first clinical gene therapy was given in 1990 to a 4-yr old girl with adenosine deaminase (ADA) deficiency.
• This enzyme is required for breakdown of deoxyadenosine into uric acids.
• In the absence of ADA toxic deoxyadenosine is accumulated and destroy the infection fighting immune cells called T-cells and B-cells.
• This disorder is caused due to the deletion of the gene for adenosine deaminase in chromosome 20.

Treatment:

• Treated by bone marrow transplantation.
• Enzyme replacement therapy, involving repeated injections of the ADA enzyme
• Lymphocytes from the blood of the patient are grown in a culture. A functional ADA cDNA is then introduced into these lymphocytes and returned into the body.
• The patient required periodic infusion of genetically engineered lymphocytes because these cells are not immortal.
• Functional ADA cDNA introduced into cells at early embryonic stages, could be the permanent cure.

Molecular diagnosis:

• Early detection of disease is not possible by conventional methods (serum and urine analysis)

Molecular diagnosis techniques:

• Recombinant DNA technology.
• Polymerase chain reaction (PCR)
• Enzyme linked Immuno-sorbent Assay (ELISA)
• Very low concentration of a bacteria or virus can be amplified and detected by PCR.
• It used to detect genetic disorders.
• PCR is use full to mutation in genes in suspected cancerous patient:
• A single stranded DNA or RNA tagged with radioactive molecule (probe) is allowed to hybridize to its complementary DNA in a clone of cells followed by detection using autoradiography.
• The clone having mutated gene unable make complementary bonding of probe, hence not appears in photographic film.

TRANSGENIC ANIMALS:

• Animals that have an alien DNA which able to express in it is called transgenic animals.

Reasons for creation of transgenic animals:

• Normal physiology and development:
• Transgenic animals are specifically designed to allow study of:
• How the genes are regulated.
• How the gene affects normal functioning of body
• How it affects growth and development. E.g. insulin like growth factor.

 

• The animals made transgenic to know the biological effect and result.

 

• Study of disease:
• Transgenic animals are designed to understand how genes contribute to the development of disease like cancers, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.

 

• Biological products:
• Transgenic animals are used to produce biological product of human interest:
• α-1-antitrypsin used to treat emphysema.
• Proteins for treatment for PKU and cystic fibrosis.
• Transgenic cow Rosie, produce human protein enriched milk (2.4 gm/lit. human α-lactalbumin)

 

• Vaccine safety:
• Transgenic mice are being developed and use in testing the safety of vaccines before they are used for humans.
• Polio vaccine is tested in mice.

 

• Chemical safety testing:
• This is also known as toxicity/safety testing.
• Transgenic animals are made to known the effect of toxic chemicals.

 ETHICAL ISSUES:

• GEAC (Genetic Engineering Approval Committee) set up by Indian Govt, which will make decisions regarding validity of GM research and safety of introducing GM-organisms for public services.
• A patent is the right granted by a government to an inventor to prevent others from commercial use of his invention.
• Patents granted for biological entities and for products derived from them; these patents are called biopatents.
• 27 documented varieties of Basmati are grown in India.
• Biopiracy is the term used to refer to the use/exploit or patent, of biological resources by multinational companies and other organizations without proper authorization from the countries and people concerned without compensatory payment.