What does animals are hierarchically organized internally mean?

Animals are hierarchically organized internally means that their bodies are made up of different levels of organization, with each level being more complex than the one below it. The hierarchy starts with cells, which are the basic unit of life. Cells are organized into tissues, which are groups of cells that perform a specific function. Tissues are organized into organs, which are collections of tissues that work together to perform a complex function. Organs are organized into organ systems, which are groups of organs that work together to maintain homeostasis, the body's internal environment. Organ systems are organized into the whole organism, which is the entire living creature.

This hierarchical organization allows animals to perform complex functions and to adapt to their environment. For example, the digestive system is responsible for breaking down food into nutrients that the body can use. The respiratory system is responsible for taking in oxygen and expelling carbon dioxide. The circulatory system is responsible for transporting nutrients and oxygen to cells and removing waste products. Each of these systems is made up of organs that work together to perform a specific function.

The hierarchical organization of animals is also evident in their development. Animals start out as a single cell, which then divides and differentiates into different types of cells. These cells then organize themselves into tissues, organs, and organ systems. The process of development is controlled by genes, which are located on chromosomes in the nucleus of cells. Genes provide the instructions for building and maintaining the body's structures.

The hierarchical organization of animals is a fundamental principle of biology. It allows animals to perform complex functions and to adapt to their environment. It is also evident in the development of animals from a single cell to a fully formed organism.