Author: Harjeet Kaur
-
Cell Division – Meiosis
Introduction Process by which chromosome number of a diploid cell (2n) is reduced to half i.e. it changes to haploid (n). Results in daughter cells differing from parent cell, genetically. Resulting haploid cell either directly becomes gamete or differentiate/divide to produce cell that later becomes a gamete. Plays a key role in eukaryotic reproduction. Homologous…
-
Cell Cycle & Cell Division – Mitosis
Key points: Chromosomes are cellular structures. They carry genes & are composed of DNA, RNA & proteins. Haploid Eukaryotic Cell contains one copy of each chromosome. Diploid Eukaryotic Cell contains two copies of each chromosome. Prokaryotic Cell divide by fission. Eukaryotic Cell divide by Mitosis & Cytokinesis. Most gametes are formed by Meiosis. ‘Cell Cycle’…
-
Prokaryotic & Eukaryotic Cells
Living World is classified into 3 division or domains, namely: 1) Bacteria (Eubacteria) 2) Archaea (Archae-bacteria) 3) Eukaryotes Bacteria & Archaea are grouped separately under Prokaryotes. Since, Viruses lack metabolic apparatus & considered non-living outside host cell, they are classified separately from the above divisions. Examples: Bacteria – Escherichia coli, Lactobacillus, Mycoplasma, Cyanobacteria etc. Archaea…
-
Potency
Definition: Ability of a particular stem cell to generate various differentiated cell types. Stem cells have ability of self renewal. In mammals, 1) Totipotent Stem Cells: Capable of forming every cell in the embryo. Also, capable of forming trophoblast cells of placenta. Example: Zygote & first 4-8 blastomeres. 2) Pluripotent Stem Cells: Capable of forming…
-
Migration of Fishes
Introduction In life history of some fishes, population needs, like foraging & reproduction, can’t be met in single habitat. So, they travel periodically from one habitat to another & back after meeting the requirement, termed as fish migration. Causes: Sexual maturity, hormonal changes, instinct, predators, competition, food, light, temperature, pH, water currents, turbidity etc. The…
-
Principles of Limiting Factors
Liebig’s Law of Minimum History: The concept was first provided by J. Von Liebig in 1840 for growth rate of plants, stating that the size & overall health of the plant depends upon the scarcest essential nutrient available to it. Later, the concept was broadened to be applicable on all organisms. Statement: Under stable conditions,…
-
Ecological Pyramids
Introduction Ecological Pyramids are graphical representation of structure & function of ecosystem at trophic levels. First described by Charles Elton, hence, also called Elton Pyramids. Show relative amounts of parameters like number, energy, biomass etc. across trophic levels. First trophic level/Producer forms the base. Successive trophic levels are represented by tiers above the base. 1)…
-
Intra- & Inter- Specific Relationship (Species Interactions)
Interactions among species is divided into two categories: Intraspecific: It is type of interaction that occurs between populations of same species. Example: Social, family, cannibalism etc. Interspecific: It is type of interaction that occurs between population of different species. Example: Parasitism, Predation, Mutualism etc. SCROLL DOWN FOR LECTURE VIDEO Interspecific Interactions The interactions are usually…
-
Trypanosoma brucei
Systematic position Trypanosoma – click here Two species of Trypanosoma brucei are known to cause diseases in humans: Note: Sub-species Trypanosoma brucei brucei does not cause infection in humans. Habitat: Blood & Lymph Habits: Obtain nourishment through osmotrophy from blood plasma. Pinocytosis occur in ‘reservoir’ at posterior end. Respiration & excretion occurs by diffusion through…
-
Productivity, Energy Flow & Efficiency – Ecosystem
(Productivity = rate of production) There are two types of productivity: Commonly used productivity unit: Primary Productivity: Producer organisms, including both photosynthetic & chemosynthetic, convert radiant energy to organic substances and the rate at which they convert is termed primary productivity i.e. Rate of conversion of radiant energy to organic substances by producers is termed…