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Conscious breathers ! Conscious breathers ! On land, human beings and other mammals breathe involuntarily. Whales and Dolphins actively decide when to breathe. Consequently, in order to breathe, they have to be conscious. Scientists have studied this phenomenon in dolphins, using electroencephalography. In this process, electrodes hooked up to the head measure electricity levels in the brain. The resulting electroencephalograms (EEGs) of dolphin brains demonstrate that in the sleep cycle, half of the dolphin's brain does indeed "shut down" while the other half is still active. Researchers have observed that dolphins are in this state for approximately eight hours a day. Let's learn different types of life process in animals.

Learning Objectives

After completing the topic, the student will be able to:

  • Describe the common features that determine why invertebrates, such as sponges, cnidarians, and flatworms, do not require a circulatory system.
  • Define and distinguish the terms invertebrate and vertebrate circulation.
  • Compare and contrast the different modes of respiration in different animals.
  • Define partial pressure and appreciate the role of partial pressure gradients in respiratory mechanism.
  • Define and distinguish the terms intracellular and extracellular digestion and identify the mode of digestion seen in different animals.
  • Describe the structure and function of photoreceptors in different invertebrates.
  • Determine how statocysts are adaptive for animals that burrow underground or live deep in the ocean.
  • Compare blood, hemolymph and hemocyanin.
Diversity of life processes Diversity of life processes Sponges and hydra are primitive animals that have no circulatory systems. Grasshopper, an arthropod has an open circulatory system.

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Life Processes

There are different life processes that are common to living things. These processes are circulation, movement, respiration, sensitivity, growth, reproduction, excretion and nutrition. Let's explore the life processes of animals in detail.

The circulatory system is a network that carries blood throughout the body. All animals except the simplest kinds have some type of circulatory system. Primitive animals like the sponge and the hydra have no circulatory systems. All their cells are in direct contact with the environment, and such a system is unnecessary. The earthworm has a closed circulatory system where blood is pumped by the heart through arteries, veins, and capillaries. Oxygen is carried by hemoglobin that is dissolved in the blood.

The grasshopper, as a representative animal of the arthropods, has an open circulatory system. After blood is pumped by the heart into an artery, it leaves the vessel and seeps through spaces called sinuses or hemocoels as it feeds body cells. The blood then moves back into a vein and circulates back to the heart. This system lacks capillaries.

Arthropod blood is clear and does not carry oxygen. The human circulatory system supplies the cells of the body with the food and oxygen needed to survive. At the same time, it carries carbon dioxide and other wastes away from the cells. The circulatory system also helps regulate body temperature and carries substances that protect the body from disease. In addition, the system transports chemical substances called hormones, which help regulate the activities of various parts of the body. There are about 100 trillion cells in the human body. For each of these cells to survive and perform its function, each cell needs to receive nutrition, replenish oxygen and remove waste. The circulatory system performs these functions for the cells.

Circulatory system Circulatory system– One of the important life processes The circulatory system in which the blood is confined to blood vessels is called closed circulatory system. The heart pumps blood through these vessels to different organs of the body. This system is efficient way of transporting blood than an open circulatory system. Few animals like earthworm, squids, octopus, and all vertebrates, like humans etc have this type of system.
The Heart

The heart is a hollow, muscular organ that pumps blood. It consists of two pumps that lie side by side. These pumps relax when taking in blood and contract as they send out blood.

The left side of the heart is a stronger pump than the right side. The stronger pump receives blood from the lungs and sends it to cells throughout the body. The weaker pump receives blood from the cells throughout the body and sends the blood to the lungs.

The Blood Vessels The blood vessels form a complicated system of connecting tubes throughout the body. The three major types of blood vessels include: Arteries that carry blood from the heart, veins that return blood to the heart and capillaries that are extremely tiny vessels that connect the arteries and the veins. The exchange of nutrients and oxygen usually occurs in the capillaries.

The blood consists chiefly of liquid called plasma and three types of solid particles known as formed elements. Plasma is made mostly of water, but it also contains proteins, minerals and other substances.

The three types of formed elements are red blood cells, white blood cells and platelets. Red blood cells carry oxygen and carbon dioxide throughout the body. White blood cells help protect the body from disease. Platelets release substances that enable blood to clot. Platelets thus aid in preventing the loss of blood from injured vessels.