OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What composed a tissue in living organisms?

1. A group of different organ systems

2. A group of similar cells

3. A collection of organelles

4. A large population of an organism

The correct answer is: A group of similar cells

A tissue in living organisms is composed of a group of similar cells that work together to perform a specific function. This understanding is fundamental to biology, as tissues represent a higher level of organization within an organism. In multicellular organisms, cells often share a common origin and perform similar tasks, which allows them to form specialized structures crucial for the organism's overall functioning. For example, muscle tissue is made up of muscle cells that contract to enable movement, while epithelial tissue consists of cells that line surfaces and protect underlying structures. This specialization of cells leads to enhanced efficiency in performing various biological activities, which is vital for the organism's survival. Choices that involve a group of different organ systems or a collection of organelles misrepresent the hierarchical organization of biological structures, as they do not reflect the cohesive nature of tissues. Similarly, referencing a large population of organisms does not align with the definition of tissue, which is focused on cellular organization and function.