Unit 7 – Genetics and Evolution

 1. Heredity and Variation

Mendelian Inheritance

• Gregor Mendel is known as the father of genetics for his work on pea plants.
• Principles of Inheritance:
• Law of Segregation: Alleles segregate during gamete formation.
• Law of Independent Assortment: Genes for different traits assort independently.

Deviations from Mendelism

1. Incomplete Dominance: The phenotype of heterozygotes is intermediate between the phenotypes of homozygotes (e.g., red and white flowers producing pink flowers).
2. Co-dominance: Both alleles in a heterozygote are fully expressed (e.g., AB blood type).
3. Multiple Alleles: More than two alleles exist for a gene (e.g., ABO blood groups).
4. Pleiotropy: A single gene affects multiple traits (e.g., sickle cell anemia affecting blood, pain, and immunity).
5. Polygenic Inheritance: Multiple genes influence a trait, resulting in a continuous range of phenotypes (e.g., skin color).

Chromosome Theory of Inheritance

• Genes are located on chromosomes, which segregate and assort independently during meiosis.

Sex Determination

• In humans, sex is determined by the presence of XY chromosomes (males) or XX chromosomes (females).
• In birds, the ZW system determines sex (ZW females, ZZ males).
• In honey bees, sex is determined by the number of chromosome sets (diploid females, haploid males).

Linkage and Crossing Over

• Genes located close together on the same chromosome tend to be inherited together (linkage).
• Crossing over during meiosis can result in genetic recombination.

Sex-linked Inheritance

• Traits linked to sex chromosomes; examples include:
• Haemophilia: A blood clotting disorder linked to the X chromosome.
• Color Blindness: A genetic condition affecting color perception, also X-linked.

Mendelian Disorders in Humans

1. Thalassemia: A blood disorder caused by reduced hemoglobin production.
2. Chromosomal Disorders:
• Down’s Syndrome: Caused by trisomy of chromosome 21.
• Turner’s Syndrome: Affects females with a missing X chromosome (45,X).
• Klinefelter’s Syndrome: Affects males with an extra X chromosome (47,XXY).

2. Molecular Basis of Inheritance

Search for Genetic Material

• Early experiments indicated that DNA is the genetic material, confirmed by studies such as those by Avery, MacLeod, and McCarty.

Structure of DNA and RNA

• DNA is a double helix composed of nucleotides (adenine, thymine, cytosine, guanine), while RNA is single-stranded and contains uracil instead of thymine.

DNA Packaging

• DNA wraps around histone proteins to form nucleosomes, which further coil to form chromatin.

DNA Replication

• Semi-conservative process where each strand serves as a template for a new complementary strand.

Central Dogma

• Describes the flow of genetic information from DNA to RNA to protein:
• Transcription: DNA → mRNA
• Translation: mRNA → Protein

Genetic Code

• The sequence of nucleotides in mRNA is translated into amino acids using codons.

Gene Expression and Regulation

• The Lac Operon in E. coli serves as a model for understanding gene regulation in prokaryotes.

Genome and Human Genome Project

• The complete set of genetic material in an organism; the Human Genome Project aimed to map all human genes.

DNA Fingerprinting

• A technique used to identify individuals based on unique patterns in their DNA.

3. Evolution

Origin of Life

• Theories about how life began on Earth include abiogenesis and panspermia.

Biological Evolution

• Change in the genetic composition of populations over generations.

Evidence for Biological Evolution:

1. Paleontology: Fossils show changes over time.
2. Comparative Anatomy: Homologous structures indicate common ancestry.
3. Embryology: Similar embryonic development suggests evolutionary relationships.
4. Molecular Evidence: Genetic similarities among species indicate evolutionary links.

Darwin’s Contribution

• Proposed natural selection as the mechanism for evolution; survival of the fittest leads to adaptation over time.

Modern Synthetic Theory of Evolution

• Integrates Darwin's theory with genetics; emphasizes mutation and gene flow as sources of variation.

Mechanisms of Evolution

1. Variation (Mutation and Recombination): Genetic diversity arises from mutations and sexual reproduction.
2. Natural Selection: Favorable traits increase an organism's chances of survival and reproduction.
• Types:
• Stabilizing Selection: Favors average traits.
• Directional Selection: Favors one extreme phenotype.
• Disruptive Selection: Favors both extreme phenotypes.
3. Gene Flow: Movement of genes between populations through migration.
4. Genetic Drift: Random changes in allele frequencies due to chance events.

Hardy-Weinberg Principle

• Describes the conditions under which allele frequencies remain constant in a population (no evolution occurs).

Adaptive Radiation

• The diversification of a group of organisms into forms filling different ecological niches.

Human Evolution

• Study of how humans evolved from ancestral primates through various stages, including bipedalism and increased brain size.

Key Diagrams

1. Structure of DNA showing nucleotide components.
2. Diagram illustrating Mendelian inheritance patterns.
3. Phylogenetic tree showing evolutionary relationships among species.

Summary

This unit covers fundamental concepts in genetics and evolution:

1. Heredity involves Mendelian principles and deviations such as co-dominance and polygenic inheritance.
2. Molecular genetics explains DNA structure, replication, transcription, translation, and gene regulation mechanisms.
3. Evolutionary biology discusses evidence supporting evolution, mechanisms like natural selection, genetic drift, and human evolution processes.

Unit 6 – Reproduction

1. Sexual Reproduction in Flowering Plants

Flower Structure

• Flowers are the reproductive structures in angiosperms.
• Male Reproductive Part: Stamen (anther and filament).
• Female Reproductive Part: Carpel/Pistil (stigma, style, ovary).

Development of Gametophytes

1. Male Gametophyte:
• Pollen grains develop in the anther.
• Microspores undergo mitosis to form two cells: generative cell and vegetative cell.
2. Female Gametophyte:
• Ovules in the ovary develop into the embryo sac.
• The megaspore undergoes mitosis to form a 7-celled, 8-nucleate embryo sac.

Pollination

• Transfer of pollen from anther to stigma.
• Types:
• Self-pollination: Pollen from the same flower or plant.
• Cross-pollination: Pollen from another flower or plant.
• Agencies: Wind, water, insects, animals.

Outbreeding Devices

• Prevent self-pollination to promote genetic diversity (e.g., dichogamy, herkogamy).

Pollen-Pistil Interaction

• Chemical signaling between pollen and pistil ensures compatibility for fertilization.

Double Fertilization

• Unique to angiosperms.
• One sperm nucleus fuses with the egg (zygote formation), and the other fuses with polar nuclei (endosperm formation).

Post-Fertilization Events

1. Endosperm Development: Provides nutrition to the developing embryo.
2. Embryo Development: Zygote develops into an embryo.
3. Seed Formation: Ovule matures into a seed.
4. Fruit Formation: Ovary develops into a fruit.

Special Modes

• Apomixis: Seed formation without fertilization.
• Parthenocarpy: Fruit formation without fertilization (e.g., banana).
• Polyembryony: Formation of multiple embryos in a seed.

2. Human Reproduction

Male Reproductive System

• Organs:
• Testes (produce sperm and testosterone).
• Epididymis, vas deferens, seminal vesicles, prostate gland, and penis.
• Testes contain seminiferous tubules where spermatogenesis occurs.

Female Reproductive System

• Organs:
• Ovaries (produce ova and hormones like estrogen and progesterone).
• Fallopian tubes, uterus, cervix, and vagina.
• Ovaries contain follicles where oogenesis occurs.

Gametogenesis

1. Spermatogenesis:
• Occurs in seminiferous tubules.
• Spermatogonia → Primary spermatocyte → Secondary spermatocyte → Spermatids → Spermatozoa.
2. Oogenesis:
• Occurs in ovaries.
• Oogonia → Primary oocyte → Secondary oocyte → Ovum.

Menstrual Cycle

• Cyclic changes in the female reproductive system (~28 days).

1. Menstrual Phase (Day 1–5): Shedding of uterine lining.
2. Follicular Phase (Day 6–14): Follicle development; estrogen secretion.
3. Ovulatory Phase (~Day 14): Release of ovum from ovary.
4. Luteal Phase (Day 15–28): Corpus luteum secretes progesterone.

Fertilization and Implantation

1. Fertilization occurs in the fallopian tube when sperm fuses with the ovum to form a zygote.
2. Zygote undergoes cleavage to form a blastocyst, which implants into the uterine wall.

Pregnancy and Placenta Formation

• Placenta forms for nutrient and gas exchange between mother and fetus.
• Hormones like hCG maintain pregnancy.

Parturition and Lactation

1. Parturition: Process of childbirth; involves uterine contractions stimulated by oxytocin.
2. Lactation: Milk production by mammary glands due to prolactin; milk ejection is stimulated by oxytocin.

3. Reproductive Health

Need for Reproductive Health

• Ensures healthy reproductive functions and prevents sexually transmitted diseases (STDs).

Birth Control Methods

1. Natural Methods: Rhythm method, withdrawal method.
2. Barrier Methods: Condoms, diaphragms.
3. Hormonal Methods: Oral contraceptives, injectables.
4. Intrauterine Devices (IUDs): Copper-T, hormonal IUDs.
5. Surgical Methods: Vasectomy (male), tubectomy (female).

Medical Termination of Pregnancy (MTP)

• Legal termination of pregnancy under medical supervision to prevent complications or unwanted pregnancies.

Amniocentesis

• Prenatal diagnostic technique to detect genetic disorders by analyzing amniotic fluid.

Infertility and Assisted Reproductive Technologies (ART)

1. IVF (In Vitro Fertilization): Fertilization outside the body; embryo transferred to uterus.
2. ZIFT (Zygote Intrafallopian Transfer): Zygote transferred to fallopian tube.
3. GIFT (Gamete Intrafallopian Transfer): Gametes transferred to fallopian tube.

Key Diagrams

1. Structure of a flower showing male and female reproductive parts.
2. Human male reproductive system anatomy.
3. Human female reproductive system anatomy.
4. Spermatogenesis and oogenesis processes.

Summary

This unit explores reproduction in plants and humans along with reproductive health:

1. Sexual reproduction in flowering plants involves gametophyte development, pollination, double fertilization, seed/fruit formation, and special modes like apomixis and parthenocarpy.
2. Human reproduction includes gametogenesis, menstrual cycle, fertilization, pregnancy, parturition, and lactation processes.
3. Reproductive health emphasizes birth control methods, prevention of STDs, infertility treatments like IVF/ZIFT/GIFT, and awareness about MTP and amniocentesis.

Unit 5 - Human Physiology

 1. Breathing and Respiration

Breathing refers to the physical process of inhaling and exhaling air, while respiration involves the biochemical breakdown of glucose to release energy.

Respiratory System in Humans

• Organs: Nose, pharynx, larynx, trachea, bronchi, lungs.
• Mechanism of Breathing:
• Inspiration: Diaphragm contracts, thoracic cavity expands, air enters lungs.
• Expiration: Diaphragm relaxes, thoracic cavity reduces, air exits lungs.
• Exchange of Gases: Occurs in alveoli via diffusion; oxygen enters blood, carbon dioxide exits.
• Transport of Gases:
• Oxygen binds to hemoglobin in RBCs to form oxyhemoglobin.
• CO₂ is transported as bicarbonate ions (70%), bound to hemoglobin (23%), and dissolved in plasma (7%).

Respiratory Volumes

• Tidal Volume (TV): Air inhaled/exhaled during normal breathing (~500 mL).
• Inspiratory Reserve Volume (IRV): Additional air inhaled (~3000 mL).
• Expiratory Reserve Volume (ERV): Additional air exhaled (~1000 mL).
• Residual Volume (RV): Air remaining after forceful exhalation (~1200 mL).

Disorders Related to Respiration

1. Asthma: Chronic inflammation causing airway narrowing.
2. Emphysema: Damage to alveoli reduces gas exchange efficiency.
3. Occupational Respiratory Disorders: Caused by exposure to pollutants (e.g., coal dust).

2. Body Fluids and Circulation

The circulatory system ensures the transport of nutrients, gases, hormones, and waste products.

Composition of Blood

1. Plasma (55%): Water, proteins (albumin, globulin), nutrients, hormones.
2. Formed Elements (45%): RBCs (oxygen transport), WBCs (immunity), platelets (clotting).

Blood Groups

• ABO system based on antigens on RBCs; Rh factor determines positive/negative blood type.

Coagulation of Blood

• Platelets release thromboplastin → Prothrombin converts to thrombin → Fibrinogen forms fibrin → Clot forms.

Human Circulatory System

1. Heart Structure:
• Four chambers: Right atrium, right ventricle, left atrium, left ventricle.
• Valves prevent backflow: Tricuspid valve (right side), bicuspid valve (left side), semilunar valves.
2. Blood Vessels:
• Arteries carry oxygenated blood; veins carry deoxygenated blood; capillaries facilitate exchange.
3. Cardiac Cycle:
• Systole (contraction) and diastole (relaxation) regulate blood flow.
4. ECG:
• P wave: Atrial depolarization.
• QRS complex: Ventricular depolarization.
• T wave: Ventricular repolarization.

Disorders of Circulatory System

1. Hypertension (high BP).
2. Coronary Artery Disease (blockage in coronary arteries).
3. Angina Pectoris (chest pain due to reduced blood flow).
4. Heart Failure (inadequate pumping by heart).

3. Excretory Products and Their Elimination

Modes of Excretion

1. Ammonotelism: Excretion of ammonia (e.g., fish).
2. Ureotelism: Excretion of urea (e.g., humans).
3. Uricotelism: Excretion of uric acid (e.g., birds).

Human Excretory System

• Organs include kidneys, ureters, urinary bladder, urethra.
• Kidney structure:
• Cortex and medulla contain nephrons.
• Nephron filters blood and forms urine.

Urine Formation

1. Filtration in Bowman’s capsule.
2. Reabsorption in proximal tubule.
3. Secretion in distal tubule.

Regulation of Kidney Function

1. Renin-Angiotensin System regulates BP and filtration rate.
2. Atrial Natriuretic Factor reduces BP by inhibiting renin.
3. ADH increases water reabsorption; deficiency causes diabetes insipidus.

Disorders Related to Excretion

1. Uraemia: Accumulation of urea in blood.
2. Renal Failure: Loss of kidney function.
3. Renal Calculi: Kidney stones.
4. Nephritis: Inflammation of kidneys.

4. Locomotion and Movement

Types of Movement

1. Ciliary movement (e.g., respiratory tract).
2. Flagellar movement (e.g., sperm cells).
3. Muscular movement.

Skeletal Muscle

• Contractile proteins:
• Actin forms thin filaments; myosin forms thick filaments.
• Muscle contraction:
• Sliding filament theory explains interaction between actin and myosin using ATP.

Skeletal System

• Functions include support, protection, movement.
• Joints allow flexibility:
• Ball-and-socket joint (shoulder).
• Hinge joint (knee).

Disorders Related to Muscular and Skeletal Systems

1. Myasthenia Gravis: Autoimmune disorder causing muscle weakness.
2. Tetany: Muscle spasms due to low calcium levels.
3. Muscular Dystrophy: Genetic disorder causing muscle degeneration.
4. Arthritis: Inflammation of joints.
5. Osteoporosis: Reduced bone density due to calcium deficiency.

5. Neural Control and Coordination

Neuron Structure

• Cell body contains nucleus and organelles.
• Dendrites receive signals; axons transmit signals.

Nervous System in Humans

1. Central Nervous System:
• Brain and spinal cord control voluntary actions.
2. Peripheral Nervous System:
• Nerves connect CNS to body parts.
3. Visceral Nervous System:
• Controls involuntary actions like digestion.

Generation and Conduction of Nerve Impulse

1. Resting potential maintained by Na⁺/K⁺ pump.
2. Action potential generated by influx of Na⁺ ions.
3. Impulse travels along axon; neurotransmitters relay signal across synapse.

6. Chemical Coordination and Regulation

Endocrine Glands and Hormones

1. Hypothalamus regulates pituitary gland activity.
2. Pituitary secretes growth hormone (GH), thyroid-stimulating hormone (TSH).
3. Thyroid produces thyroxine (T₄) for metabolism regulation.
4. Adrenal glands secrete adrenaline for stress response.
5. Pancreas secretes insulin for glucose regulation.

Mechanism of Hormone Action

Hormones bind to specific receptors on target cells to initiate cellular responses.

Disorders Related to Endocrine System

1. Dwarfism (GH deficiency).
2. Acromegaly (GH excess).
3. Cretinism (thyroxine deficiency in children).
4. Goiter (iodine deficiency).
5. Diabetes Mellitus (insulin deficiency).
6. Addison’s Disease (adrenal cortex insufficiency).

Key Diagrams

1. Structure of human heart showing chambers and valves.
2. Nephron structure explaining filtration process.
3. Sliding filament model for muscle contraction.

Summary

Human physiology integrates multiple systems working together to maintain homeostasis:

1. Respiratory system ensures oxygen supply and CO₂ removal.
2. Circulatory system transports nutrients and gases efficiently while regulating heart activity.
3. Excretory system eliminates waste products while maintaining water balance.
4. Locomotion involves coordinated movements supported by muscles and bones.
5. Nervous system controls voluntary/involuntary actions via neurons and impulses.
6. Endocrine system regulates metabolic activities through hormones acting as messengers.