Mitosis, Meiosis, and Ecosystem Roles: Producers to Decomposers

Mitosis: Cell Division Explained

Mitosis is the process where a single cell divides into two identical daughter cells. DNA is duplicated, creating two identical nuclei. This process ensures each new cell receives a complete set of chromosomes.

Mitosis Phases

• Prophase: Chromosomes condense and become visible. The nuclear membrane breaks down.
• Metaphase: Chromosomes align along the metaphase plate in the center of the cell.
• Anaphase: Sister chromatids separate and move to opposite poles of the cell.
• Telophase: The nuclear membrane reforms around the separated chromosomes, and the cytoplasm divides (cytokinesis), resulting in two identical daughter cells (diploid).

Meiosis: Sexual Reproduction and Genetic Diversity

Meiosis is a type of cell division that results in four daughter cells each with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Meiosis Phases

• In the first division, the number of chromosomes is halved.
• Exchange of genes occurs between homologous chromosomes, increasing genetic diversity.
• Chromosomes migrate to opposite poles to begin the second division.
• The second division results in the formation of gametes. Gametes in plants and animals are haploid, containing half the number of chromosomes.

Ecosystem Roles: Producers, Consumers, and Decomposers

Different organisms obtain energy and nutrients from the environment in diverse ways. They can be grouped into:

Producers

Producers are autotrophic organisms that manufacture their own organic matter from inorganic substances.

Consumers

Consumers are heterotrophic organisms that feed on organic matter. There are different types:

• Herbivores: Also called primary consumers, they feed on plants.
• Carnivores: Secondary, tertiary, or quaternary consumers that feed on other animals.
• Omnivores: Consume both plants and animals.

Decomposers

Decomposers are heterotrophic organisms that feed on detritus (dead organic matter and waste products) and transform it into inorganic compounds.

Some small animals are detritivores; although they do not completely transform the detritus into inorganic materials, they prepare it for the final action of decomposers.

Carbon Fixation

Plants use the chemical energy from the light phase to reduce CO2, nitrates, and sulfates and assimilate bioelements (C, H, S) to synthesize carbohydrates and amino acids. Plants obtain CO2 from the air through the stomata of their leaves. The carbon reduction process is cyclic and is known as the Calvin Cycle.

CO2 fixation occurs in three phases:

1. Carboxylation: A CO2 molecule binds to ribulose-1,5-bisphosphate (a 5-carbon molecule), forming an unstable 6-carbon compound that splits into two molecules of 3-phosphoglycerate (PGA).
2. Reduction: 3-phosphoglycerate is reduced to glyceraldehyde-3-phosphate (PGAL), using ATP and NADPH.
3. Regeneration/Synthesis: Glyceraldehyde-3-phosphate molecules follow different pathways; five out of six molecules are used to regenerate ribulose-1,5-bisphosphate.