Human Sensory System and Locomotion: A Comprehensive Guide
Receiver Sensitivity
Stimulus
Environmental changes detectable by our body are called stimuli. These stimuli are detected by sensitive nerve cells called receptors.
Types of Receptors
There are two types of receptors: internal receptors (interoreceptors) and external receptors (exteroreceptors).
Internal receptors inform us about the state and function of our internal organs. External receptors, located on the body’s surface, detect external stimuli.
Receptor Classification
- Mechanoreceptors: React to pressure
The Biology of Monera, Protista, Fungi, and Plants
Kingdom Monera
Bacteria: These organisms are prokaryotic, unicellular, and the first on Earth. They include:
- Eubacteria: Green bacteria are photoautotrophs that don’t produce O2 and have bacteriochlorophyll.
- Proteobacteria: A broad group of gram-negative bacteria, including photosynthetic and heterotrophic types like Legionella.
- Spirochetes: Gram-negative bacteria without chlorophyll (e.g., Spirochaeta sicilis).
- Cyanobacteria (Blue-Green Algae): Photosynthetic bacteria with chlorophyll, ancestors of
Protein and Carbohydrate Classification and Functions
Proteins and Carbohydrates
Holoproteins
Fibrous Proteins
Coiled along a single dimension. Insoluble in water, with structural or protective functions.
- Collagen: The main component of connective tissue, and is present as one of the main components of the extracellular matrix of the skin.
- Myosin: A fibrous protein responsible for muscle contraction.
- Keratins: A large group of animal proteins that are synthesized and stored in the cells of the epidermis: they form horns, nails, hair, and wool in many animals.
Early Organic Synthesis Experiments & The Origin of Life
Synthesis of Organic Compounds in the Lab
Early Experiments Simulating Prebiotic Conditions
1. Stanley Miller’s Experiment
Stanley Miller designed an experiment to simulate early Earth’s atmosphere. He placed a mixture of gases (methane, ammonia, hydrogen, and water vapor) in a closed system and subjected it to electrical sparks to simulate lightning. After a week, he analyzed the products and found that organic compounds, including amino acids, had been synthesized. This experiment supported the idea
Read MoreIntroduction to Cell Biology: Structure and Function
Introduction to Cell Biology
The Origin of Life
In 1992, biochemists revisited Oparin and Haldane’s hypothesis on the processes of chemical evolution during the origin of life. According to them, organic molecules could be formed from atmospheric gases reacting with each other due to solar radiation. These new organic molecules would fall into the oceans to form what they called the primordial soup. The molecules would then associate with each other, forming coacervates. This hypothesis was largely
Read MorePregnancy Stages, Development & Changes: A Guide
Fertilization
The process by which two gametes fuse to create a new individual with a genome derived from both parents.
It is caused by the entry of the sperm inside the egg, which then forms a coating around it that prevents fertilization by a second sperm.
Nesting
The fertilized egg travels to the uterus and implants in the uterine membrane, which has been previously prepared by hormone action to welcome, shelter, and nourish it. At this time, the embryo consists of two distinct classes of cells:
- One