Comprehensive IB Biology SL & HL Syllabus

Surface area to volume relativity ratio limits the size of the cell – More the surface area, more will be the movement of the materials in/out of the cell.

Specific genes are involved in the production of certain types of cells, with each cell having the complete genetic information of the organism.

Stem cells are the origin cells, from where the cell division starts and also they retain their ability to differentiate into various cell types. Different types of stem cells

Structural parts of a prokaryotic:

• Cell wall and plasma membrane
• Pili and Flagella
• Ribosomes
• Nucleoid Region

 and eukaryotic cells:

• Cell wall
• Cytoplasm
• Ribosomes
• Endoplasmic Reticulum
• Golgi Apparatus
• Lysosomes
• Mitochondria
• Nucleus
• Chloroplasts
• Centrosomes
• Vacuoles

Eukaryotic cells in animals and plants

Cholesterol molecules are not present in the plant cells but in animal cells.

Two distinctive areas of Phospholipid bilayers are termed as hydrophilic (water-loving) and hydrophobic (water-fearing)

• Sodium-potassium pump

Passive membrane transport: Does not require energy

• Diffusion – Movement of substance occurs from an area of higher concentration
  to lower concentration across a membrane
• Facilitated diffusion – Involves the membrane bound proteins to aid movement of substance across the membrane. The protein acts as a “carrier protein”
• Osmosis –  It involves the movement across the partially permeable membrane due to concentration gradient

Endocytosis and exocytosis: Endocytosis allows the molecules to enter the cell while exocytosis allows them to leave the cell. Fluidity (provided by bilayer structure) of the membrane is essential for these processes.

The first cells must have arisen from non-living material.

The origin of eukaryotic cells can be explained by the endosymbiotic theory.

Mitosis is the division of the nucleus into two genetically identical daughter nuclei.

The division of cytoplasm into two daughter cytoplasmic cells is called cytokinesis.

Cyclins mediate the cell cycle by binding to cyclin-dependent protein kinases (CDKs). Cyclins are involved in the control of the cell cycle.

• Interphase
• Mitosis
• Prophase
• Metaphase
• Anaphase
• TeloPhase
• Cytokinesis

An uncontrolled division of cells causes a cluster of unwanted cells in an area called tumour. Two types are found; primary tumour and secondary tumour.

Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

Metabolism: Inside a cell, in an aqueous medium many molecular collisions occur, these collisions provide energy for the reactants to undergo chemical reactions.

Anabolism is the synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions.

Catabolism is the breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers.

Properties: Cohesive, adhesive, thermal, solvent, and  high boiling point

Water works on the principle “like dissolves like” and dissolves only polar solutes, being polar molecules. These polar solutes are called hydrophilic.

Hydrophobic (water-fearing) solutes like methane (CH4) do not dissolve in the water because they are non-polar.

When a hydrocarbon long chain has a carboxyl group at one end and a methyl group at the other, it is called saturated fatty acids.

If one double bond exists in the chain of hydrocarbons, the fatty acid is then called monounsaturated fatty acids.

When two or more double bonds are present, then it is called polyunsaturated fatty acids.

Lipids get hydrolysed into two carbon segments which ultimately fulfil the energy requirements by the production of ATP through cellular respiration.

There are 20 different types of amino acids out of which 16 are polar and 4 are non-polar

Ribosomes link these amino acids together and form polypeptides which can be of huge numbers.

Two or more polypeptides bond together to perform a particular function, together they are considered as protein.

Structure of proteins goes from the simple primary to the globular quaternary.

Examples of proteins: Insulin, Collagen, Rubisco, Haemoglobin, etc

They have an active site on which the substrate binds. Substrates and their active sites are specific for each other.

Factors affecting enzymatic reactions:

• Temperature
• pH
• Substrate concentration

Immobilised enzyme: These enzymes are trapped in tiny pores on beads of calcium alginate.

Immobilised enzymes are used for the production of lactose-free milk.

DNA contains deoxyribose pentose sugar while RNA contains Ribose pentose sugar.

DNA differs from RNA in the number of strands present, the base composition and the type of pentose.

Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase.

Translation is the Process of synthesis of polypeptide with the help of cell organelle, ribosome.

• Three types of RNA are used in this process namely;
    ○ mRNa: Has genetic information for the formation of polypeptide
    ○ rRNA: Makes up the ribosomal protein and support the formation of polypeptides
    ○ tRNA: It has an anticodon loop that has bases complementary to the code. These are specific for each amino acid.

Glycolysis is the method of slow oxidation of the glucose using various enzymes.

Fermentation is of two types; alcoholic fermentation and lactic acid fermentation

Aerobic pathway of cell respiration: It involves complete oxidation of glucose into water + CO2 + ATPs.

In the leaves of the plants, there is a presence of green colour organelle called chloroplast which contains the light absorbing pigment chlorophyll in it

Photosynthesis gives off the oxygen and in the cellular respiration oxygen is taken in.

Photosynthetic rate is affected by many external factors like light, temperature and CO2 concentrations. These are also called the limiting factors of the photosynthesis

Alleles: These are the versions or a form of gene, differs with only one or few bases.

Mutation: It is a sudden random change in the genetic material.

The complete set of an organism’s base sequences of DNA is called its genome.

The Human Genome Project was begun in 1990, with the aim to find all the base sequences of the human genome.

When the cell is not dividing, the chromosomes (condensed form) are not visible, but the chromatin is there in the nucleus.

Two chromosomes with the same kind of genes like in 23 pairs of human cell chromosomes.

Ploidy is the number of sets of chromosomes that exist in a cell:

1. Haploid (n); having only one set of chromosomes
2. Diploid (2n); having two sets of chromosomes
3. Triploid (3n); having three sets of chromosomes

Karyotype is the picture of the chromosome of an individual and karyogram is the standard representation of the chromosomes in the order, according to shapes and sizes.

The 23rd pair of chromosome is sex chromosome, as it determines the sex of the individual.

Meiosis I and II

Down’s syndrome is one of the disorders and caused by an additional copy of chromosome number 21 i.e. when the 21st chromosome fails to separate during Anaphase I, creating trisomy of 21st chromosomes in the offspring.

Gametes receive one of the two alleles of a specific gene. And this allele could be dominant or recessive with respect to the other allele.

• Dominant alleles: These alleles always express themselves in the phenotype over the other.
• Recessive alleles: These are the alleles which get masked by the dominant allele i.e. can’t express themselves in the presence of dominant allele.

There are two kinds of genetic diseases in humans:

• Autosomal genetic: The disease caused by alteration in genetic material of autosomal cells rather than sex cells
• Sex-linked: The disease caused by alteration in an allele found on either of the sex chromosomes X or Y

Polymerase chain reaction: This technique is used to amplify the gene of interest obtained from gel electrophoresis, using a thermocycler.

DNA Profiling: This is the process for matching an unknown sample of DNA with a known sample to see if they correspond.

The technique of transferring a gene of interest from one organism (donor organism) to other organism (host organism) to modify them in search of availing more benefits, also called as recombinant DNA technology.

Clones: These are the exact copy of the individuals already exist, made by using genetic techniques

Genetically Modified Organisms (GMOs) are called transgenic plants or transgenic animals

Ecosystem: Sum total of biotic and abiotic components of a particular geographical area being integrated through exchange of energy and nutrient cycling.

Decomposers are the organisms which help in breakdown of the organic waste material and dead animal and plant matter into inorganic useful material.

Species: It is a group of organisms that can interbreed and produce fertile offspring

Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion.

Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion.

The interlinking of two or many food chains is called food web.

Autotrophs absorb the sunlight and take up inorganic nutrients from the soil to make organic food for the rest of the food chain.

This loss of the energy is in the form of heat which can’t be used ever again but then contributes to global warming.

Methanogens (members of Archaea) produce methane (CH4) as a waste gas while metabolizing its food.

Methane is found in natural gas and its oxidation produces CO2

Peat is a dark coloured, waterlogged soil mixture of dead organic matter, found in wetlands.

Limestone: Many organisms in the oceans takes up the dissolved CO2 from the water and form their carbonated shells and coral polyps takes up the carbonate ions and calcium which combines to form calcium carbonate

Greenhouse gases (GHGs) include water vapour, CO2, CH4, nitrous oxide (NO2) etc
Light-colored objects absorb much less of the sunlight and reflect it back but dark coloured objects absorb much of the sunlight and get more warmer than light coloured objects.

Fossils are the petrified remains or traces of animals and plants and the accumulated evidence from these remains are called fossil record.

Adaptive Radiation refers to the development of different functional structures from a common ancestral form.

Animal Breeding: The breeding of animals and plants is done artificially by selecting the best individual with the desired traits and crossing them to get the product with the desired trait.

Homologous structures: The structures which are anatomically the same but perform different functions and focus on common ancestors.

Adaptive radiation: It refers to the development of different functional structures from a common ancestral form.

Sudden drastic change in the DNA sequence due to external or internal factors which produces variation in an organism is called mutation.

Meiosis: Random orientation of the chromosomes at metaphase offers variation every time the gamete forms.

The organism that is well adapted to its environment has better chances of survival than the one which is less adapted.

All the organisms that exist or existed (with the exception of viruses because they are considered as non-living) are classified into three domains namely; Archaea domain, Eubacteria domain and Eukaryote domain.

Further classification occurs by classification of the organism into seven different taxa: Kingdom, Phylum, Class, Order, Family, Genus and Species

Plant and Animal Phyla

Vertebrates are classified into class: Fish, Amphibians, Reptiles, Birds and Mammals

Two types of traits: Plesiomorphic and Apomorphic traits

Mutations in organisms occur roughly at the same rate and therefore the number of differences in sequence can be used to deduce how long ago species split from a common ancestor. This is how it works as an evolutionary or molecular clock.

Cladograms are tree diagrams that show the most probable sequence of divergence in clades.

Pancreas: It is a Multipurpose organ which produces two hormones named insulin and glucagon which metabolise glucose and pancreatic juice.

Liver: It is the largest organ in the human body. The hepatic lobules are the structural and functional units of liver, from where bile juice is secreted into the small intestine for digestion purposes.

Small Intestine: It is a four-layered tubular structure with the lumen and villi (facing lumen) on the innermost layer mucosa.

Each villus contains a capillary bed for absorbing and transport of digested monomers.

Veins: These blood vessels take blood from different organs of the body towards the heart.

Capillaries are single-celled thick therefore the blood cells enter the capillaries at the rate of one cell at a time.

Right side of the heart offers pulmonary circulation and the left side of the heart offers systemic circulation.

A specialized tissue called sinoatrial node (SA node) is present in the right atrium, it is also known as pacemaker. SA node has the properties of both muscles and nervous system.

Atrial systole: The sinoatrial node generates the signals and both the atria go into contraction

Ventricular systole: The atria relaxes (atrial diastole) but the ventricles now contract

The lub and dub sound (heart beat), the heart makes comes from the closure of the atrioventricular valves and the semilunar valves respectively.

Skin and mucous membranes offers the major primary defence towards the
pathogens.

Secondary defence: When the pathogens somehow pass through these primary physical barriers then it comes into action.

Leucocytes (WBC) are the cells that tackles pathogens provides immunity against them

Antibodies are the Y-shaped protein molecules which help in fighting against the invading foreign cells

Antibiotics: It disfigures the biochemistry of the bacterial cell wall and deactivates them in such a way to stop their metabolism in many ways without harming the human eukaryotic cells which lack a cell wall.

The filling and expiration of the air in and from the lungs is called ventilation.

Inspiration: While breathing in diaphragm contracts, external intercostal muscles with abdominal muscle raise the rib cage to increase the volume of thorax.

Journey of air: Trachea → Left and right primary bronchi → smaller branches of bronchi → bronchioles → alveoli.

Type I pneumocytes: Thin, large membrane surface area, capable of diffusion and if damaged cannot be replaced due to incapability of performing mitosis.

Type II pneumocytes: Thick, cuboidal, have smaller membrane surface area. They produce surfactants which prevents alveolus membrane from sticking together.

The highly developed nervous system has neurons with myelin sheath around axons, called myelinated neurons. And other kind does not have myelin sheath around axons and are called non-myelinated neuron

When a voltage or potential difference is maintained across the membrane and the neuron is not transmitting any impulse then it is called resting potential of that neuron.

Action potential is the nerve impulse and consists of depolarization and repolarization.

Repolarization: It is the change from positive to negative by opening of the potassium ions and closing of the sodium ions at the same time.

Hormones are the non-nutrient chemical messengers which are produced in trace amounts.

Thyroxin: Produced and secreted by butterfly-shaped thyroid gland.

Leptin (appetite-controlling hormone): Produced by adipose tissue in the body. More fat, the more the secretion of leptin into the blood.

Melatonin: Produced by pineal gland present in the brain and helps to maintain the 24-hour cycle of activity called the circadian rhythm.

Insulin and Glucagon: Produced and secreted by pancreas and regulates blood sugar levels.

Human Reproduction: It involves the fusion of male gamete (sperm) and female gamete (egg) to form a zygote

Sex determination: Male has XY pair and female has XX pair of chromosome.

Menstrual Cycle: It is the hormonal cycle that begins after hitting puberty in human females. Each cycle lasts for approximately 28 days however, it differs from person to person.

• Hormones involved:
    ○ FSH and LH: They increase the production of estrogen
    ○ Progesterone: After ovulation, corpus luteum secretes progesterone which helps in thickening of the endometrium.
    ○ Oestrogen: The oestrogen is released as to provide a negative feedback by signalling hypothalamus to stop secretion of GnRH

In vitro fertilisation: It is a method of artificial reproduction in which egg and sperm are fertilised in vitro

DNA is a double stranded structure, with each strand consisting of alternating deoxyribose sugar and phosphate molecules as a backbone.

There are 4 nitrogenous bases: Adenine and Guanine (Purines) and Cytosine and Thymine (Pyrimidines)

The negatively charged DNA wrapped around the positively charged histones to make a bead-like structure called the nucleosome.

DNA Replication: This process occurs during the cell division in which the DNA content is doubled. This is also an enzyme catalysed process involves helicase and DNA polymerase

Genes are present on the DNA inside the nucleus and the protein synthesis occurs outside the nucleus in the cytoplasm. Therefore the mRNA (messenger RNA) acts as the intermediary molecule to transfer the information for protein synthesis from nucleoplasm to cytoplasm.

The strand which has the same base sequence as that of mRNA (while having uracil in the place of thymine) is called sense strand. And the other template which has a complementary base sequence is called antisense DNA strand.

Slicing: This is post-transcription process for removal of non-coding sequence called introns
from the pre-mRNA, so that only exons remain.

Methylation of any gene expression could prevent transcription

Process: Initiation, Elongation, Translocation and then repeats

Two or more polypeptides bond together to perform a particular function, together they are considered as protein.

All the organisms are found to be genetically different due to specific DNA sequences called the genome and so their proteome.

Structure of proteins goes from the simple primary to the globular quaternary. It possesses a three-dimensional shape (specific shape for the particular function).

• Metabolism is the sum of all the chemical reactions taking place inside a living organism, most of which are enzyme-mediated reactions.
• Catabolism and Anabolism
• Enzymes lower the activation energy of the reaction, without altering the reactant or product proportions.
• The inhibition of an enzymatic activity occurs due to change in certain factors including pH, temperature and substrate concentration. Types: Competitive and Non-competitive
• End product inhibition: Many metabolic reactions occur in an assembly-line type of process with each step catalysed by an enzyme to achieve the end product.

The reduced molecule has much more potential energy than the oxidised form of molecule, therefore the energy is released when the glucose gets oxidised.

Glycolysis is the method of slow oxidation of the glucose using various enzymes

If no oxygen is available, the pyruvate molecules enter the anaerobic pathway followed by fermentation.

There is a direct transfer of a phosphate group from a phosphate bearing molecule (phosphoenolpyruvate) to ADP in order to make ATP. The process is called substrate-level phosphorylation.

Krebs cycle

Electron Transport Chain – It is the series of protein complexes called cytochromes and organic molecules to pass on the electrons from one member of the chain to another in a series of redox reactions.

The coenzymes NADH and FADH2 released in previous cycles act as the sources of electrons. NADH allows the production of three ATPs and FADH2 allows the production of 2 ATP molecules.

Chemiosmosis is the process in which movement of protons occurs to provide energy for phosphorylation.

An enzyme called ATP synthase is embedded in the inner membranes of the mitochondria which facilitates ions across.

Light Dependent reactions:

• It is a non-cyclic reaction that occurs in thylakoids and the stack of thylakoids is called granum.
• Presence of pigments like chlorophyll, xanthophyll and carotenoids
• The organized structure of these pigments in the thylakoid membrane is called a photosystem.
• Photosystem contains even more complex structures within which is the reaction centre.
• Photosystem I and Photosystem II

Light Independent reactions:

• It happens at night and occurs in the stroma of the chloroplast.

18 molecules of ATP and 12 molecules of NADPH are necessary to produce one molecule of glucose.

Adhesion: It is the force of attraction between the molecules of different substances

Xylem: It is involved in supporting the plant and act as water conducting tissue of terrestrial plants.

Stomatal Activity: Stomatal pores open and close by change in the turgor pressure in the guard cells

Cohesion-tension theory: This theory explains the movement of fluid in plants. It takes into account the concentration gradients, cohesion between the water molecules, adhesion between the water molecules and walls of the xylem and tension created by all these phenomena.

Roots absorb water and mineral ions necessary for plant growth which can be done passively, actively or by the action of fungal hyphae.

Phloem translocates molecules in various directions inside the plant but follows the principle of source to sink flow.

Sugar is loaded in the sieve tube from the source (leaves). The formation of concentration gradients forces water from surrounding cells to enter the sieve tube as well.

Water uptake inside the sieve tube creates hydrostatic pressure which helps in flowing of the sugar to the sink (any fruit or root).

Meristematic tissue composed of cells which have the ability to divide on its own by keeping one cell as its origin.

Apical meristems: These are the primary meristems occurring at the tips of roots and stems. The developing tip tissue with apical meristem collectively called as shoot apex.

Lateral meristems: These are responsible for secondary growth which allows growth in the thickness of plants.

Hormones are the chemical messengers and in plants they are released in response to an environmental stimulus.

Auxins are the group of plant hormones that can be produced artificially but produced naturally at apices of stems and roots. They influence the tropism of the plant.

The growth of the plant in response to light is called phototropism.

Monocots and Dicots

Four basic flower parts: Sepals, Petals, Stamen and Carpel

Pollination: It is the process by which pollen grains from the anther lands on the stigma of the same or another flower by means of wind, insects, water, birds etc

Fertilization: It is the process of union of male and female sex cells to form a unit called zygote.

Seeds: These are the structures that keep the embryo functional and protected.

Plants react to the sunlight as they grow. This reaction to light features three types of flowering: Long-day plants, Short-day plants, Day-neutral plants

Phytochrome is the pigment in the plants to offer control by light.

Crossing over: Exchange in DNA material between non-sister chromatids. It is an enzyme-mediated process and the enzyme involved is recombinase.

Chiasma forms while crossing over. It is a point of adherence of two non-sister chromatids for efficient exchange of genetic material.

Crossing over produces new combinations of alleles on the chromosomes of the haploid cells.

Law of independent assortment: It states that the separation of one pair of alleles between the daughter cells is independent of another pair of alleles.

When two genes are found on the same chromosome they are called linked. The tendency of these genes to pass on to the next generation together is called linkage.

Continuous variation deals with the spectrum of phenotypes and shows an unbroken range of phenotypes of a particular character.

While discontinuous variation deals with few phenotypes and can show two or more forms of a particular character.

Chi squared tests: These are the tests done to actually check the accuracy of possible ratios come by crossing.

Change in the allele frequency leads to evolution.

Hardy-Weinberg equation; It is the equation to calculate the allele frequency, genotypes or phenotypes within a population.

Variation in allelic frequency by natural factors leads to different types of selection of equilibrium: Directional, Stabilising, Disruptive

Some factors cause the hindrance in a major proportion which fall apart the populations and causes barrier in reproducing together: Geographical, Temporal and Behavioural

All the reproductive isolation factors lead to speciation

The rate of speciation can be judge by two ways: Gradualism and punctuated equilibrium

Antigens are polysaccharide and proteins, present on the surface of the cell.

Immune response:

• Macrophages: These are massive leukocyte cells, which engulfs the pathogen by the process called phagocytosis
• T lymphocytes recognise the antigen presentation and become activated
• T lymphocytes bind to B lymphocytes and simulate them to produce specific antibodies

B cells are less in number while initiating the response but they clone themselves (undergo mitosis) to produce large amounts of antibodies.

Histamines are the chemical which causes allergy symptoms like sneezing, congestion, itching, red skin etc. i.e. histamines are the cause of allergy.

Memory cells stream in blood vessels but remain inactive until the pathogen it is specific to, attacks again.

Vaccine: A vaccine contains attenuated or killed pathogens or their derivatives to generate the primary response in human’s body against the pathogen

Monoclonal antibodies are specific antibodies for only one type of antigens i.e. they are exactly the same.

B cells are fused with cancer cells called myeloma cells so that the leukocytes remain alive for a long time. The fusion of B cells and myeloma cells makes up hybridoma cells (hybrids of antibody producing cells and are long-lived myeloma cells).

Some bones act as levers to facilitate movements of some bony parts.

Muscles work antagonistically in pairs to contract and relax at the same time, causing movement of the bone.

Bone-to-bone joints are:

• Synovial joints: These are the joints with a lubricant called synovial fluid
• Ball and socket joint
• Hinge joint

Muscle is composed of thousands of cells called muscle fibre. They are multinucleated and have specialised endoplasmic reticulum.

There occur many parallel elongated structures called myofibrils inside the muscle fibre which is packed with the mitochondria to provide ATP at the time of muscle contraction.

Myofibril is made up of sarcomere units which give it dark and light bands.

Myosin gives dark shade and actin gives light shade.

An action potential is generated by the nervous system carried by motor neurons to the sarcolemma.

Ca+ ions bind to the troponin protein which stimulates the tropomyosin to slide over & uncover the binding sites of actin.

Insects have specialised structures called Malpighian tubules. These tubules are close from one end and open from the other, the blood travels inside the tube and undergoes selective reabsorption.

Kidneys filter blood and separate out the waste products. It produces urine which is a combination liquid of water and waste products (from the blood).

Nephrons are the constituents of the kidney.

Renal artery brings unfiltered blood to the kidney and renal vein takes filtered blood away from the kidney.

Parts of nephron; glomerulus, Bowman’s capsule (surrounding the glomerulus), proximal convoluted tubule (PCT), loop of Henle, distal convoluted tubule (DCT) and a peritubular capillary bed surrounding these tubules.

Filtrate flows into the lumen of single-celled thick PCT which is lined by microvilli for better reabsorption.

The response mechanism of the body to maintain the water balance is called osmoregulation

Loop of Henle has two portions; descending portion and ascending portion

ADH (antidiuretic hormone) is secreted from the posterior pituitary and makes collecting duct permeable to water so that excess water moves out due to osmosis

The animals which are having different solute concentrations compared with that of the environment are called osmoregulators.

The animals which have same solute concentrations as that of surrounding environment are called osmoconformers

The process of formation of ovum is called oogenesis.

Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and differentiation.

The fusion of male and female gametes is called fertilisation. It can be internal or external

Human fertilisation: Millions of sperms are ejaculated at the time of copulation, which travel into the
fallopian tube where the egg is present to fertilise it.

Implantation: After fertilisation, mitotic division starts. It is now called blastocyst with a surrounding layer called trophoblast.

Placenta is formed from mother and embryonic tissue. The exchange of fresh nutritive blood and deoxygenated blood with waste products occurs through the blood vessels in the umbilical cord of the placenta.

Embryo secretes hCG hormone which enters the mother’s bloodstream and maintains the hormonal balance, which further releases the progesterone to maintain the endometrium corpus luteum.

A small amount of oxytocin hormone is released by pituitary which causes uterine contractions.

Contractions signal to release more oxytocin. Uterine contractions lead to parturition (baby comes out).

The process of formation or synthesis of neurons by differentiation of the neuroblast cell is called neurogenesis.

An axon grows from each immature neuron in response to chemical stimuli.

Mechanism of elongation of the axon of the neuron: A growth cone is present at the tip of the axon which directs it. Target cells are present at the final position of the neurons which produce chemical messages, to which the neuron responds by forming the synapse.

Multiple synapses are formed during early brain development

Neural pruning: The removal of unneeded connections eventually at the adult stage with the help of microglia cells and it leads to better brain efficiency.

Plasticity of the nervous system: It signifies that the brain has the ability to reform and adapt according to perform functions as per need. 2 types: Functional and Structural

The neural tube has two ends; Anterior end and Posterior end, which develop into the forebrain and rest of the other parts of the brain, respectively.

Different parts of the brain constitutes to different functions

Brain and spinal cord are parts of the CNS (Central Nervous System), the other parts are covered by PNS (Peripheral Nervous System).

ANS is further divided into sympathetic and parasympathetic systems.

When a person shows no movements of extremities like legs and arms, no eye movement, absence of corneal reflex, absence of pupil reflex, absence of gag reflex, no respiration then the person is considered to be brain dead.

The cerebral cortex covers the largest part of the mature brain i.e. cerebrum, formed from the front part of the neural tube.

The left cerebral hemisphere receives sensory input and controls muscle contraction

• Mechanoreceptors
• Proprioceptors
• Chemoreceptors
• Thermoreceptors
• Photoreceptors

All these receptors send messages to the central nervous system, which process the signals.

Retina- Photoreceptor cells are present here. Rod cells receives very dim light enables black and white vision while cone cells receives bright light

The light falling on this retina travels through ganglion cell layer, bipolar cell layer and then the receptors rod and cone cells which then transfer information through the nerve fibres to the brain.

The bones in the middle ear, malleus, incus and stapes receive vibrational sound

The semicircular canals help in maintaining the equilibrium.

Taxis: It is a directed response to a stimulus.

Kinesis: It is the response of an organism towards non-directional stimulus like some factor surrounding them such as humidity.

Learned behaviour: It is not genetically inherited but develops as a result of experience by time.

Imprinting: It is a rapid learning process by which an organism develops attraction and recognition of another moving object regardless of the consequences.

Operant conditioning: It creates an association between behaviour and its consequences for an animal.

Memory: It is the process of encoding the information, storing it and then accessing it while putting it into use.

Neurons communicate through synapses using neurotransmitters

Types of neurotransmitters (NTs) according to the responses they show; excitatory and inhibitory neurotransmitters.

Types of neurotransmitters (NTs) according to the rate of activity; slow-acting NTs and fast-acting NTs.

Psychoactive drugs: These drugs affect the postsynaptic transmission and thereby alter the functioning of
these synapses.

Drug addiction: It may be defined as the cravings and intake of the drugs again and again due to loss of control or limiting.

Anaesthetics: These are the molecules that can block the sensory reception and cause loss of sensation in any part or the whole body.

Natural selection also influences the animal behaviour.

The genes of these microorganisms can be altered to increase their performance

Pathway engineering: It is a method to alter or modify the genetic makeup of the microorganism to derive the products for human use.

The process of large scale culture of microorganism to produce metabolites of interest using fermenters

There are two types of fermentation; fed-batch and continuous fermentation.

Anaerobic microbes work in the production of biogas by breaking down organic matter such as manure, plant matter and household organic wastes.

Gram staining: It is a method of differentiating two groups of bacteria named; gram-negative and gram-positive bacteria.

When a new gene is introduced in a species that offers production of the proteins that were not the part of its proteome earlier is called transgene and the organism possessing this gene is called transgenic.

Genetically modification in crops may offer certain benefits like increased crop yields

Recombinant DNA can be introduced by direct physical and chemical methods or indirectly by vectors.

Means to transfer desired genes:

• Physical methods: Electropolation, Biolistics, Microinjection
• Chemical methods: Transfection, Lipofection

A biofilm is a film of aggregates of microorganisms that sticks to the surface due to cooperation between individual cells.

Emergent properties: These are the properties shown by biofilms as a consequence of the unity of many different types of microorganism. Properties can be complex structures, Quorum sensing and resistance to antimicrobial agents.

Advantages of biofilms include trickle filter beds and cleaning of water bodies

The marker alleles are found more frequently in people affected with any disease.

DNA microarray: It is a small surface having a collection of DNA probes attached to it which can be used to identify the genetic marker.

Polymerase Chain Reaction: It is the most prominent tool in biotechnology to amplify any strand of DNA.

ELISA: It is also a diagnostic tool, may be used to diagnose HIV and to test the presence of drug in blood and urine.

Tracking experiments are done using a reporting element like green fluorescent protein (GFP) or radioactive probes to track the location or interaction of the protein molecule rolling inside the body.

Gene Therapy: In this technique the viral vector could be retrovirus or adenovirus.

Genetically modified animals or transgenic animals are also the means of biopharming.

EST: It is a small fragment cDNA and can be used to locate or to determine the sequence of the gene

Cladograms and Phylograms: These tools can help in constructing evolutionary relationship trees.

BLAST: ​​It is a tool used to search the databases and to find the regions of similarities between sequences

BLASTn is for the nucleotide search whereas BLASTp is for the protein search, it compares the protein sequences.

When more than one species inhabits an area then it is called population.

Group of populations living together and interacting with each other is called a community.

Abiotic and biotic factors sometimes act as limiting factors which results in distribution of the species according to their tolerance of limiting factors.

Keystone species: These are the species with high significance to maintain an ecological community.

When two species in an area depend upon the same limited resource and if one of them gets a slight advantage, will be better adapted.

Interspecific interactions:

• Herbivory: An interaction between plants and animals
• Predation: One is predator and the other is prey
• Parasitism: One organism is host and the other is a parasite that lives in or on the body of the host
• Mutualism: Two species live in a close association and both of them benefit each other.
• Commensalism: One organism benefits from the other which is neither harmed nor benefitted in any way.

Transect is a method of sampling a population of plants or animals along a longitudinal section of an ecosystem.

This available energy at each level is called net production

Biomass is the calculation of dry weight present at each trophic level. It also gets lost at every trophic level because during cell respiration glucose is broken down into CO2 and water which gets excreted out of the body.

Ecological succession: It is the change in the abiotic and biotic factors in an ecosystem over time. 2 types: Primary and secondary

Gersmehl diagrams: These are the representational diagrams that demonstrate inter-relationship between the nutrient stores in an ecosystem.

Biome is the division of the biosphere which has well developed vegetation and extensive community

In a closed ecosystem, energy can be exchanged but not the matter.

Alien species become invasive, because they have resources, they reproduce and multiply, increasing the risk of extinction of many species and they have no predator of their own.

Biomagnification is the process of accumulation of chemical substances in higher trophic levels.

Two kinds of plastics found in the ocean that are considered extremely harmful for marine populations; Microscopic plastic and macroscopic plastic.

Indicator species: These species are sensitive to the environment and therefore used to assess the specific environmental conditions.

Biotic index: It tells the relative frequency of the indicator species with respect to its surroundings

There are two methods of conservation;

• In situ conservation: Endangered species are kept in their well-adapted habitat without the interference of any invasive species.
• Ex situ conservation: Species are kept in personalised care apart from its natural habitat, due to its high risk of extinction.

There are three biogeographical factors which influence the diversity: Latitude gradient, Elevation gradient, Area effect

Edge effect: It is shown when two borderline ecosystems overlap each other and therefore influence each other.

When a habitat has limited supply of resources then an S-shaped (sigmoid) curve graph is shown by the population. Three stages: Exponential growth phase, Transition phase and Plateau phase

Carrying capacity (K): It is the maximum number of individuals supported by a habitat. 2 limiting factors: Bottom-up or Top-down

To estimate an animal population in an ecosystem, capture-mark-release-recapture method is used.

The nitrates then travel into the roots of the plants by expenditure of energy (ATP). These are used to make proteins in the plants called assimilation.

Denitrifying bacteria such as Pseudomonas denitrificans reduce nitrate and nitrite back into the nitrogen gas to be released into the environment.

Phosphorus is found in marine sediments and mineral deposits and is a main component of DNA, RNA and ATP. Slow weathering of sedimentary rocks releases phosphorus into the soil from where it is taken by plants.

Amino acids: Out of total 20 amino acids, 9 are essential amino acids which us be supplied in our regular diet

Minerals: These are the inorganic substances which are mostly taken in the ionic form (i.e. as electrolytes) and are needed in very small quantities.

Vitamins: These are organic molecules, which are taken as part of diet but many of them are also synthesised in our body.

Fatty acids: Omega-3 and omega-6 are the two essential fatty acids that need to be taken in our diet.

Malnutrition is the result of intake of an unbalanced or improper diet. The diet can be unbalanced or fail to provide essential nutrients leading to starvation, or it may have excess amounts of carbohydrates and fats leading to overweight.

Consequences of overweight: Hypertension, Type II Diabetes

There are three glandular secretions; HCl, pepsin and mucus which are produced by three glandular cells present in the gastric pits.

Gastrin (a hormone secreted by endocrine gland) is also released due to this response which results in even more secretion of HCl and pepsinogen.

Helicobacter pylori neutralises the acid in the stomach but causes its own infection that leads to gastritis and ulcers or even cancer if prolonged.

Absorption of the digested food occurs in the small intestine lined by villi. Villi further contain projections called microvilli for even better absorption.

Molecules absorbed in two ways: Active Transport Mechanism and Pinocytic vessels

The capillaries of the liver which receives blood from the two blood vessels are called sinusoids.

Specialised leukocyte cells called Kupffer cells are present inside the sinusoids which help in recycling of older erythrocytes by breaking down its haemoglobin.

Liver:

• Removes toxins from the blood
• Regulates nutrients in the blood
• Helps in recycling of erythrocytes
• Secretes bile and plasma proteins

The liver intercepts blood from the gut to regulate nutrient levels.

Two atrioventricular valves on left and right side of the heart, separating left atrium from the left ventricle and right atrium from the right ventricle. These two valves are called bicuspid or mitral valve and tricuspid valve respectively of the left and right side.

The sounds of the heart i.e. lub and dub comes from the closure of these valves timely.

Veins have valves which prevents the backflow of the blood

A specialised tissue called sinoatrial node (SA node) is present in the right atrium, it is also known as pacemaker.

When SA nodes send signals, the Atrioventricular (AV) node receives it with a delay and sends the signal for the contraction of both the ventricles. The synchrony between the atria and ventricular contraction is maintained by these electrical signals.

When the heart stops working (cardiac arrest) or is no longer in sequence with the set of electrical impulses of a cardiac cycle (arrhythmia), defibrillators could be used.

Thrombosis: A condition in which a clot is formed within a blood vessel causing blockage.

There are two values of blood pressure; systolic pressure (when arteries are contracting) and diastolic pressure (when arteries are resting).

Endocrine glands include Pituitary, Thyroid, Adrenal, etc

2 types of hormones:

• Steroid: Synthesised from cholesterol and therefore have the properties of lipid. The receptor protein for hormones is present inside the cytoplasm.
• Peptide: These are composed of amino acids and therefore have the properties of proteins.

The Pituitary gland is called the master gland because it secretes most of the hormones to stimulate a certain function in the body. Two lobes that act as glands: Posterior and Anterior

Hormones are produced in the hypothalamus and travelled down to the pituitary to be secreted.

Hormones secreted by the pituitary gland controls growth, any developmental changes, reproduction and homeostasis

Myoglobin molecules can occupy only one oxygen molecule.

Foetal haemoglobin has much more affinity for oxygen than adult haemoglobin

Carbon dioxide transport: It is dissolved in blood plasma in some amount, some is carried by haemoglobin (causing Bohr shift) and most of it is converted into bicarbonate ions.

Ventilation rate is controlled by the respiratory centre in medulla oblongata.

Chemosensors are present in the inner walls of aorta and carotid arteries, which detect the CO2 levels in the blood