Cells and Evolution
Table of Contents
1 Important Contributions
| Epithet/Discovery | Person |
|---|---|
| Father of Biology | Aristotle |
| Father of Medicine | Hippocrates |
| Father of Genetics | Gregor Mendel |
| Blood circulation | William Harvey |
| DNA Fingerprinting | Alec Jeffreys |
| Pencillin | Alexander Fleming |
| Vaccination (small pox) | Edward Jenner |
1.1 Charles Darwin
- wrote On the Origin of Species
- in which he proposed the theory of Natural Selection
- which stemmed from his work carried out during his voyage aboard HMS Beagle.
- His work was greatly influenced by his observations at Galapagos Islands (Pacific Ocean) off the coast of present day Ecuador.
2 Cell Biology
- Cell theory proposed by Schleiden and Schwann.
| Smallest cell | Mycoplasma (bacteria) |
| Largest cell | Ostrich egg |
| Longest cell | Neuron |
2.1 Types of organelles
2.1.1 Organelles with double membrane
- Mitochondria
- Nucleus
- Chloplasts/plastids (in plant cell only)
2.1.2 Organelles without any membrane
- Centriole - play a role in cell division
- Ribosomes - site of protein synthesis
2.1.3 Organelles bound by a single (unit) membrane
- Golgi bodies - secretion and intracellular transport
- Endoplasmic reticulum - transporting proteins
- Lysosomes - intracellular digestion, breaks down metabolic wastes into reusable material
2.2 Cell Wall
- found only in plant cells, bacteria and fungi
- provides shape and rigidity
| Type of life | material of cell wall |
|---|---|
| Plants | cellulose, lignin |
| Fungi | chitin |
| Bacteria | peptido-glytin |
2.3 Cell Membrane
- selectively permeable membrane
- made of phospholipids
- regulates movement of molecules inside and outside the cell
2.4 Mitochondria - Respiration
- site of cell respiration
- aka powerhouse of the cell
- the process of aerobic respiration is known as Krebs Cycle
- Adenosine Triphosphate (ATP) is produced from ADP
Mitochondria has DNA, RNA and enzymes of its own. It functions like a cell within a cell and its division is carried out independently of the division of the larger cell.
2.5 Lysosome (suicidal sacs) - Digestion
- cell digestion (contains hydrolytic enzymes)
- disintegrate metablic wastes into reusable molecules
2.6 Ribosomes
- synthesize polypeptides (proteins) from amino acids
- structure and function studied by Venkatraman Ramakrishnan (Nobel Prize)
2.7 Plastids
- occur in plant cells
- of 3 types
- chloroplast - photosynthesis
- chromoplast - give colour to flowers, fruits
- leucoplasts - storage of starch
2.8 Golgi Bodies
- also known as dictiosome
- role in storage and processing of materials
- more in number in plants cells
2.9 Vacuoles
- larger size in plant cells
- provide turgor pressure
- store toxins and metabolic wastes
2.10 Cilia and Flagella
- help in movement of the cell
- cilia are more in number but smaller
- flagella is longer but singular
2.11 RNA & DNA
| RNA | DNA |
|---|---|
| single stranded | double-stranded |
| contains uracil | contains adenine, thumine, guanine, cyctosine bases but not uracil |
| present in nucleaus as well as in cytoplasm | present only inside the nucleus |
3 Evolution
3.1 Chronological evolution of molecules in nature
- Nitrogen
- Ammonia
- Methane
- Sugars
- Proteins
- Prokaryotes
3.2 Summary of origin of life
- Free atoms(C, H, O, N, P)
- Origin of molecules and simple inorganic compounds (water, ammonia, hydrogen)
- early organic compounds (methane, HCN)
- simple organic compounds (simple sugars, fatty acids, amino acids, nitrogen bases)
- complex organic compounds (carbohydrates, lipids, proteins, nucleic acids)
- co-acervates (aggregates of previous organic compounds)
- prokaryotes (bacteria)
- eukaryotes
3.3 Theories of evolution
| Name of scientist | Book | Proposition |
|---|---|---|
| Lamarck | Philosophie Zoologique | Inheritence of acquired characteristics |
| Darwin | On the Origin of Species | Inheritance of useful variations by natural selection |
| Hugo de Vries | Mutation theory – sudden discontinuous variations |
3.4 Classification of organs
| Homologous organs | Analogous organs | Vestigal organs |
|---|---|---|
| same structure, different function | different structure, same function | organs present in reduced forms |
| forelimbs in frog, lizard, pigeon, whale | wings of birds and insects | vermiform appendix |
| mouth parts of insects | sting of honeybee and scorpion | wisdom tooth |
| fins of fishes and whales | nictitaping membrane | |
| caudal vertebrae |