The body of all complex animals is organised into how many basic types of tissues that form organs and organ systems?

Introduction / Context:
Although animals are made up of many different specialised cells, these cells can be grouped into a small number of basic tissue types based on structure and function. These tissues then combine to form organs and organ systems. This question assesses your understanding of how many fundamental tissue types are recognised in complex animals such as humans.

Given Data / Assumptions:

• The question refers to complex animals, including humans and other vertebrates.

• It asks for the number of basic tissue types.

• Options range from very large numbers like 4000 down to small numbers such as 4 and 2.

• We assume knowledge of standard textbook classification of animal tissues.

Concept / Approach:
In zoology and histology, cells in complex animals are organised into four basic tissue types: epithelial tissue, connective tissue, muscular tissue, and nervous tissue. Each type has multiple subtypes and specialisations, but they all fall into these four broad categories. For example, blood and bone are connective tissues, while cardiac and skeletal muscles are muscular tissues. Thus, despite the large variety of cell types, only four fundamental tissue groups are recognised at the basic level.

Step-by-Step Solution:
Step 1: Recall that epithelial tissue covers body surfaces and lines body cavities and organs. Step 2: Recognise that connective tissue supports, binds, and protects other tissues and includes bone, cartilage, blood, and adipose tissue. Step 3: Understand that muscular tissue is specialised for contraction and movement and includes skeletal, smooth, and cardiac muscle. Step 4: Identify nervous tissue as the type that conducts impulses and coordinates body functions, composed of neurons and supporting cells. Step 5: Group these into the standard four categories used in animal histology: epithelial, connective, muscular, and nervous. Step 6: Compare this with the options given and see that 4 matches the known number of basic tissue types. Step 7: Recognise that numbers like 40, 400, or 4000 are far too large and refer instead to the number of different cell types or subtypes, not fundamental tissue categories.

Verification / Alternative check:
Standard biology and anatomy textbooks introduce animal tissues in a chapter that explicitly lists four basic tissue types. Diagrams and tables then explain the different forms and functions of each group. Advanced texts may describe many specialised subtypes but still organise them under these four headings. This consistent teaching across educational levels confirms that complex animals have four basic tissue types.

Why Other Options Are Wrong:

4000: There are many thousands of distinct proteins and many cell variations, but not thousands of basic tissue categories.

400: Similarly, there are not hundreds of fundamental tissue types; this number is unrealistic at the basic classification level.

40: Some classification schemes may identify numerous subtypes of tissues, but the core grouping remains four.

2: Too few to account for the clear functional and structural differences between epithelial, connective, muscular, and nervous tissues.

Common Pitfalls:
Learners may confuse the number of tissue types with the number of organs or cell types. Because the body is complex, it is tempting to think there must be many basic tissue types. Another pitfall is to lump tissues together too broadly and underestimate the standard grouping of four. Remembering the names of the four categories and their key roles helps fix the correct number in memory.

Final Answer:
The body of all complex animals consists of 4 basic types of tissues.