Characteristics and Formation of Living Things: A Comprehensive Guide
Characteristics of Living Things
- Complexity: Composed of numerous molecules.
- Cells: Unicellular and multicellular organisms.
- Life Functions:
- Nutrition: Obtaining matter and energy.
- Relation: Interaction with the environment.
- Reproduction: Producing offspring.
Formation of Living Things
Formed by chemical compounds similar to bioelements (e.g., carbon, hydrogen, oxygen, nitrogen) called biomolecules.
Types of Biomolecules
- Inorganic: Water and minerals (carbonates, phosphates).
- Organic: All contain carbon.
- Carbohydrates:
Introduction to Genetic Engineering
4) Cellular Structural Proteins and Nucleic Acids
Nucleic Acids
DNA is a double helix formed by the repetition of four molecules called bases: adenine, guanine, cytosine, and thymine. These bases contain nitrogen. The size of a DNA molecule is measured in bases, kilobases, or megabases. DNA is shaped like a spiral staircase. Its railings are formed by each of the two strands, with monotonous successions of the four components of the DNA alphabet: A, C, G, and T. The steps of the staircase are chemical
Read MoreStimuli, Responses, and Reproduction in Plants and Animals
Stimuli and Responses in Living Things
How Living Things Respond to Stimuli
Behavior is the sequence of actions triggered by a stimulus that causes a response. The organs producing a response are called effectors.
Movement: Predominantly in animals, involving muscle contractions.
Production of Substances: Glands produce secretions like sweat, saliva, and tears.
Responses in Plants
Tropisms: Changes in the direction of plant growth.
- Positive Tropism: Growth towards the stimulus.
- Negative Tropism: Growth
Understanding the Structure and Function of Cells
Cells: Exploring the Building Blocks of Life
Cell Structures and Their Functions
Eukaryotic Cells
Eukaryotic cells are characterized by a distinct nucleus enclosed within a membrane. These cells also contain various organelles, each with a specific role:
- Mitochondria: Double-membraned organelles responsible for energy production through cellular respiration.
- Nucleus: Houses the cell’s genetic material (DNA) organized into chromosomes.
- Golgi Apparatus: Processes and packages proteins and lipids.
- Cytoplasm:
Origin and Evolution of Life
1. Origin of Life
1.1 What is a Living Being?
– All living things are organized around something called a cell.
– In human beings, there are six main chemical elements: C, H2O, N2, P, S.
– The organic molecules are:
- Carbohydrates (containing C, H2, and O)
- Lipids (containing C, H2, and O)
- Proteins (C, H2, O, N2, S)
- Nucleic acids (C, H2, O, N2, P)
1.2 The Germinal Theory
Spontaneous Generation Theory: Human beings may appear from inanimate matter.
Pasteur (1822-1895): He demonstrated that living organisms could
Plant and Animal Tissues: Structure and Function
Plant Tissues
1. Meristematic Tissues
These small, polyhedral cells have thin walls, few vacuoles, and are found in apical and lateral meristems.
Apical Meristems
Responsible for primary growth (lengthening) at the tips of roots and stems.
Lateral Meristems
Responsible for secondary growth (thickening). Two types:
- Vascular Cambium: Produces vascular tissues.
- Cork Cambium: Produces cork (suber).
2. Permanent Tissues
Organized into three systems:
Ground System
- Parenchyma: Living cells.
- Collenchyma: Living cells