Organs in Multi-cellular Organisms

Grade 7 Science Worksheets

What is the order of the levels of organization in a multicellular organism?

All multi cellular organisms like large animals and human beings have various organ systems that work together, carrying out activities that keep us alive.

The body has various smaller units that build and work together. For any living being to live, eat and develop themselves all organs of the body must function properly for example the digestive, nervous systems, circulatory system.

The timely activity of all the organs helps all the systems to function efficiently. For example, circulatory system circulates blood. If it didn’t transport blood on time. It affects the entire body.

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Multi and unicellular beings and their organ systems

Why are there different types of cells in the body of multi-cellular organisms?

Human beings are multi cellular organisms. We have complex bodies and have more than 30 trillion cells; these cells are not in direct contact with the outer environment. These cells are incapable of absorbing nourishment’s directly from the environment.

Unlike single–celled organisms like euglena, amoeba which has a tendency to breed in a place rich in nutrition. It directly and easily absorbs nutrients from the environment. It gets its oxygen to perform body functions that also gets easily absorbed or diffused into its cell through its cell membrane, and also carbon dioxide and other wastes gets out in the same way. For reproduction, it easily just divides itself in two.

A Picture of an amoeba

Such easy processes does not happen with the cells present in large multi cellular organisms but they get their nutrition from a source which is an enclosed fluid called extracellular fluid a fluid found just outside of cells. The cells receive oxygen and nutrients from this fluid and release waste products into it.

All organ systems carry out their assigned functions. For example, our respiratory system along with our circulatory system helps to take in oxygen and lets out carbon dioxide; our digestive system digests and processes food. The skeletal system makes our movement possible; the endocrine system secretes hormones; and the excretory system gets rid of food waste.

Organs of the human body

Cardiovascular System

It helps maintain body temperature and pH levels meaning potential of hydrogen, this helps to control acid levels and alkalinity in our body. Cardiovascular system also transports oxygen and nutrients, to the cells and removes wastes and CO2 from the same.

Organ tissues that are involved are: heart blood and blood vessels.

Digestive System

Its main function is to digest food and absorb the nutrients, minerals, vitamins, carbohydrates, protein and water from the food taken in.

Organ tissues that aid are: Mouth, salivary gland, food pipe or esophagus, stomach, liver, pancreas, gall bladder, small intestine, large intestine.

Lymphatic System

Helps to defend against dangerous infection and diseases and transfers lymph between tissues and the blood vessels.

Organ Tissues that aid are: Lymph nodes, and lymph vessels

Endocrine System

The Endocrine System develops a communication process within the body with the help hormones and makes long-term change in other organ systems.

Tissue systems that connect are: Pituitary gland, thyroid, parathyroid, adrenals, testes, and ovaries.

Muscular system

Muscular system helps us to move around, support, flexibility and mobility of the body.

Tissues involved: smooth muscles and skeletal muscles.

Nervous System

The nervous system mainly picks up required data and transfers that for information processing. It then sends and receives the data from the central nervous system (brain).

Organs involved are: brain, sensory nerves, spinal cord.

Reproductive System

Produces gametes and sex cells, embryo to produce offspring or young ones

Organs involved: male body has prostate, and penis. Female body has ovaries, uterus.

Respiratory system

It is a set of organs and tissue systems which help to take in air rich in oxygen and exhaling air rich in carbon dioxide.

Organs involved: Mouth, nose, larynx, pharynx, lungs, bronchi

Skeletal System

It protects soft underlying tissues of the body, provides for flexibility and movement to the joints. It produces cells carrying blood, and stores the nutrients.

Organs involved: Joint muscles, cartilage, tendon, and ligament.

Urinary System

This system removes excess water and salts, natural acids and controls the ph level (potential of hydrogen) of the body.

Organs: Kidneys, urethra, urinary bladder, ureters.

Immune System

The immune system fights against micro pathogens and basically the disease-causing antibodies and other diseases.

Tissue systems which work here are leukocytes, thymus, spleen, tonsils, also other skin tissues.

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Check Point

I. Describe the functions of the following:

Immune system
Nervous system
Lymphatic system
Endocrine system
Cardiovascular system

Answer Key

I. Describe the functions of the following –

Immune System: Fights against micro pathogens, disease-causing antibodies and other diseases.

Nervous System: The nervous system mainly picks up required data and transfers that for information processing. It then sends and receives the data from the central nervous system (brain).

Lymphatic System: Helps to defend against dangerous infection and diseases and transfers lymph between tissues and the blood vessels.

Endocrine System: Develops a communication process within the body with the help hormones and makes long-term change in other organ systems.

Cardiovascular System: It helps maintain body temperature and pH levels that is acid levels in our body. This means potential of hydrogen. It also transports oxygen and nutrients, to the cells and removes wastes and CO2 from the same.

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