Explain the role and importance of a food web in an ecosystem and list 5 differences between mitosis and meiosis.

3a)
A food web illustrates the feeding relationships between different organisms in an ecosystem. It shows how energy and nutrients flow through the ecosystem.

The importance of a food web in an ecosystem:

• It demonstrates the interconnectedness of species, showing how changes in one population can affect others.
• It helps maintain ecosystem stability by providing multiple food sources for consumers, reducing the impact of a decline in any single food source.
• It facilitates the transfer of energy from producers to consumers and decomposers, ensuring the cycling of nutrients.
• It helps regulate population sizes of different species, preventing overpopulation of any single species.
• It indicates the health of an ecosystem; a complex food web suggests a more resilient and diverse ecosystem.

3b)
Here are 5 differences between mitosis and meiosis:

1. Number of divisions: Mitosis involves one cell division, while meiosis involves two cell divisions (meiosis I and meiosis II).
2. Number of daughter cells: Mitosis produces two daughter cells, whereas meiosis produces four daughter cells.
3. Chromosome number: Daughter cells from mitosis are diploid ($2n$), having the same number of chromosomes as the parent cell. Daughter cells from meiosis are haploid ($n$), having half the number of chromosomes as the parent cell.
4. Genetic identity: Daughter cells from mitosis are genetically identical to the parent cell and to each other. Daughter cells from meiosis are genetically different from the parent cell and from each other due to crossing over and independent assortment.
5. Purpose: Mitosis is for growth, repair, and asexual reproduction. Meiosis is for sexual reproduction, producing gametes (sperm and egg cells).

3c)
The importance of mitosis:

• Growth: Mitosis increases the number of cells, allowing multicellular organisms to grow from a single zygote.
• Repair and Replacement: It replaces damaged or worn-out cells, such as skin cells or blood cells, maintaining tissue integrity.
• Asexual Reproduction: In some organisms, mitosis is the primary method of reproduction, producing genetically identical offspring.

4a)
Here are 4 adaptations of the ileum for absorption:

1. Long length: The ileum is very long, providing a large surface area for absorption.
2. Villi: The inner surface is folded into numerous finger-like projections called villi, which further increase the surface area.
3. Microvilli: The epithelial cells lining the villi have microscopic folds on their surface called microvilli, creating a brush border that vastly increases the surface area for absorption.
4. Rich blood supply: Each villus contains a rich network of blood capillaries to efficiently transport absorbed nutrients away from the small intestine.
5. Thin walls: The walls of the villi are only one cell thick, allowing for a short diffusion distance for nutrients to pass into the bloodstream or lymphatic system.

4b)
One function of each in digestion:

• Stomach: Produces gastric juice containing hydrochloric acid and enzymes (like pepsin) to begin protein digestion and kill bacteria. It also churns food to mix it with digestive juices.
• Liver: Produces bile, which emulsifies fats in the small intestine, aiding in their digestion and absorption. It also processes absorbed nutrients and detoxifies harmful substances.
• Pancreas: Produces pancreatic juice containing digestive enzymes (e.g., amylase, lipase, trypsin) that break down carbohydrates, fats, and proteins in the small intestine. It also produces hormones like insulin and glucagon.

4c)
Two functions of bile:

1. Emulsification of fats: Bile salts break down large fat globules into smaller droplets, increasing their surface area for enzymatic digestion by lipase.
2. Neutralization of chyme: Bile is alkaline and helps neutralize the acidic chyme entering the duodenum from the stomach, providing an optimal pH for pancreatic enzymes to function.

5a)
Tissue fluid is formed when plasma leaks out of the capillaries.