MYP Biology 2.2 Tissues Notes

How Are Cells Organized in Multicellular Organisms?

1. Multicellular organisms don't function as loose collections of cells.
2. Instead, cells are arranged in a hierarchical structure, where each level builds on the one below:
   1. Cells form tissues,
   2. Tissues form organs,
   3. And organs form organ systems.

How Do Specialized Cells Form Tissues?

1. Tissues form when many cells of the same type organise themselves to cooperate.
2. This cooperation allows tissues to perform tasks that no single cell can manage alone.
3. For example, one muscle cell contracts weakly, but millions together create strong movement.The structure of the tissue always reflects its function.

What Are the Main Tissue Types in Animals?

1. All animal tissues fall into four major categories, each serving a distinct biological purpose.
2. The table below summarizes them clearly.

Note

All four tissue types appear in most organs, but in different proportions depending on the organ’s purpose.

What Are the Main Tissue Types in Plants?

1. Plant tissues are organized differently from animal tissues because plants do not move and have different survival needs.
2. Plant tissue types include:

Tip

• Mesophyll tissue contains many chloroplasts.
• This is why most photosynthesis happens in the leaves, not roots.