Understanding Living Organisms: From Cells to Kingdoms

Understanding Living Organisms: Core Concepts

Origin and Development of Life

• Animals born from eggs are called oviparous.
• Those that arise from the mother's body are called viviparous.
• Plants may arise from seeds or spores.
• Fungi are always born from spores.

Nutrition: How Organisms Obtain Energy

Plants are living beings that possess chlorophyll, which enables them to make simple substances like water, carbon dioxide, and some minerals. This process is called photosynthesis and is performed using solar light.

Organisms obtain food in various ways:

• Herbivores eat plants.
• Carnivores eat animals.
• Omnivores eat both plants and animals.

Respiration

All living organisms breathe to sustain life processes.

Reproduction Strategies

The primary form of reproduction is sexual reproduction. In this, there are distinct male and female individuals, a concept known as the separation of sexes. An individual possessing both male and female reproductive organs simultaneously is called a hermaphrodite.

Some living organisms also exhibit asexual reproduction, which does not involve two sexes. In asexual reproduction, a complete individual can develop from a portion of another individual.

Interaction and Response

Living organisms interact with their environment and respond to stimuli.

The Cell: Basic Unit of Life

Unicellular vs. Multicellular Organisms

• Organisms formed by a single cell are called unicellular.
• Those with many different types of cells are called multicellular.

Key Cellular Components

The shape and size of living things are very different, but all are composed of tiny units called cells.

• Cell Membrane: This surrounds and protects the cell, allowing the passage of certain substances.
• Cytoplasm: Primarily composed of water, it fills the cell.
• Nucleus: Contains the genetic information to regulate the cell's functions.
• Cell Wall: Plant cells, in addition to a cell membrane, also possess a rigid cell wall.

Prokaryotic vs. Eukaryotic Cells

Bacteria, for example, have much smaller cells without a nucleus; these are called prokaryotic cells. This differentiates them from more complex cells that possess a nucleus, known as eukaryotic cells.

Major Kingdoms of Life and Classification

Living organisms exhibit immense diversity, ranging from those formed by a single cell and heterotrophic nutrition to others composed of millions of cells and autotrophic capabilities.

Key Characteristics of Life's Kingdoms

• Animal Kingdom: Consists of multicellular organisms with heterotrophic nutrition, sensitivity, and the ability to move.
• Plant Kingdom: Comprises multicellular organisms that are autotrophic, meaning they produce their own food through photosynthesis.
• Fungi Kingdom: Lacks chlorophyll, making them heterotrophic (they absorb nutrients from their environment). They are generally not able to move.

Classification: Monera and Protista

• Kingdom Monera (Bacteria): These are the simplest microorganisms, lacking a nucleus (prokaryotic).
• Kingdom Protista: This kingdom includes single-celled organisms that possess a nucleus (eukaryotic). Within the Protista kingdom, there are two main groups:
  • Protozoa: These are organisms consisting of a eukaryotic cell. All protozoa are heterotrophic, feeding on bacteria or remains of living organisms. They often live in aquatic environments, and some can cause diseases like malaria.
  • Algae: A group of organisms that normally live in water. Their cells are always eukaryotic, possessing plastids with photosynthetic pigments like chlorophyll.

Biological Classification Hierarchy

In biological classification, the Kingdom is a larger grouping, while Species is the smallest group into which living things are classified.