Animal Diversity: Symmetry, Body Cavities, and Major Taxa
1. Types of Symmetry in Animals
Radial Symmetry
- Description: Body parts arranged around a central axis.
- Examples:
- Jellyfish (Phylum Cnidaria): Radial symmetry aids in floating and detecting prey from all directions.
- Sea Anemones (Phylum Cnidaria): Allows equal interaction with the environment on all sides.
- Starfish (Phylum Echinodermata): Helps in movement and interaction with the environment.
- Sea Urchins (Phylum Echinodermata): Spines radiate from a central point.
- Advantages:
- Can interact with the environment
Sensory Receptors, Nervous System, and Endocrine Functions in Animals
Sensory Receptors
Receptors are cells specialized in capturing certain stimuli and transforming them into nerve impulses.
Characteristics
- Specificity or differential sensitivity: Each type of receptor is sensitive to a particular stimulus.
- Range: Each stimulus needs to act for long enough and at a certain intensity.
- Adaptation: The ability of certain receptors, when a stimulus persists for some time, to soften or eliminate the intensity of feeling.
Cell Types
The cells may be:
- Epithelial: In this case,
Cellular Evolution: From Atoms to Complex Life Forms
The Origins of Life: A Cellular Journey
We are mammals, but our biological history began long before millions of years.
The Big Bang occurred approximately 20 billion years ago, forming galaxies and planets. It took one hundred thousand years for the universe to cool after so many explosions!
Our home, the Earth, is about 4 billion years old.
Inorganic molecules began interacting with each other. Gas, water, solids, lightning, and thunderstorms accelerated chemical reactions with their energy, leading
Read MoreLamarck vs. Darwin: Evolution, Natural Selection, and Adaptation
Lamarck’s Incorrect Ideas on Adaptation
a) Web-Footed Legs in Ducks
Lamarck’s flawed explanation:
- Ducks developed webbed feet by constantly swimming.
- Living things strive for perfection.
- Useful features are developed through effort.
- Acquired traits are passed to offspring.
b) Reduced Eyes in Moles
Lamarck’s flawed explanation:
- Moles reduced their eyes by not using them.
- Living things strive for perfection.
- Useful features are developed through effort.
- Acquired traits are passed to offspring.
- Unused features
Metabolism, Plant Tissues, and Respiration
Metabolism: Catabolism and Anabolism
Catabolism is the transformation of biomolecules into simple and complex molecules, storing chemical energy released as phosphate bonds and ATP molecules. This process destroys molecules with high-energy covalent bonds through exothermic chemical reactions. Catabolism is the reverse of anabolism.
Anabolism or biosynthesis is a part of metabolism responsible for synthesizing complex organic molecules (biomolecules) from simpler ones or nutrients. It requires energy
Read MoreMicrobiology: Culture, Preservation, Growth, and More
Types of Culture Media
Culture media provide nutrients to support the growth of microorganisms. Their types depend on physical consistency, composition, and intended purpose:
Based on Consistency:
- Liquid Media:
- Lacks agar and is entirely liquid. Used for growing large bacterial populations.
- Example: Nutrient Broth, often used for maintaining stock cultures.
- Solid Media:
- Contains 1.5–2% agar to solidify the medium. Solid media allow for bacterial isolation into distinct colonies.
- Example: Blood Agar, which