Levels of Organization Chapter Notes | Science for Grade 6 PDF Download

Introduction

The chapter "Levels of Organization" explains how the human body and plants are made up of tiny parts called cells that work together to keep living things alive. Just like tiny dots in a painting come together to make a picture, cells group together to form larger structures in our bodies and in plants. This chapter explores how cells form tissues, organs, and organ systems, and how these parts work together to help organisms function. It also talks about important topics like bone marrow transplants and organ donation, showing how science helps people stay healthy.

How are your cells organized to make up your body?

• Your body is made up of tiny parts called cells that work together to keep you alive.
• Cells in your body are grouped in a special way to form larger structures, similar to how tiny dots in pointillism art form a picture.
• Scientists estimate there are about 37.2 trillion cells in your body.
• All these cells are organized to help your body work properly.

How are cells organized in the body?

• Organisms can be unicellular (made of one cell) or multicellular (made of many cells).
• The human body has about trillion cells.
• Multicellular organisms have different types of cells, each with a specific job, like muscle cells, nerve cells, or blood cells.
• As organisms grow, cells divide to make new cells through a process called cell differentiation.
• Cell differentiation allows cells to become specialized, like turning into muscle cells, nerve cells, or blood cells.
• Similar cells group together to form larger structures in the body.

Tissues

• Cells group together to form tissues, which are groups of similar cells that work together for a specific task.
• Humans have four main types of tissues:
  • Muscle tissue: Helps the body move, like contracting the stomach for digestion.
  • Connective tissue: Gives structure and support, connecting other tissues.
  • Nervous tissue: Carries messages to and from the brain.
  • Epithelial tissue: Forms the protective outer layer of skin and lines internal body parts.
• Plants have three main types of tissues:
  • Dermal tissue: Protects the plant and reduces water loss.
  • Vascular tissue: Moves water and nutrients throughout the plant.
  • Ground tissue: Provides storage, support, and is where photosynthesis happens.

Bone Marrow Transplants: Why might you need new bone marrow?

• Healthy blood cells are important for the body’s health.
• Red blood cells carry oxygen around the body.
• White blood cells fight infections.
• Platelets help stop bleeding.
• Bone marrow is a tissue inside some bones that makes blood cells.
• Diseases like leukemia or sickle cell disease can affect bone marrow, making it hard to produce healthy blood cells.
• A bone marrow transplant can treat these diseases by replacing unhealthy bone marrow with healthy bone marrow.
• In a transplant, the patient’s unhealthy bone marrow is destroyed, and healthy bone marrow is introduced.
• The healthy bone marrow can come from the patient (treated) or a donor.
• Donor bone marrow is taken from the pelvic (hip) bone in a process called harvesting.
• The donor’s body replaces the harvested bone marrow, so there are no long-term effects for the donor.
• The new bone marrow is put into the patient’s bloodstream and moves to the bone cavities to produce healthy blood cells.

How are tissues organized in the body?

Similar cells group together to form tissues, like fat, which is a type of connective tissue. Tissues are organized to form larger parts of the body.

Organs

• Organs are groups of different tissues that work together to do a specific job.
• For example, the stomach is an organ that breaks down food and is made of:
  • Muscle tissue: Contracts to break up food.
  • Epithelial tissue: Lines the stomach.
  • Nervous tissue: Sends signals to show when the stomach is full.
  • Connective tissue: Supports the stomach wall.
• Plants also have organs, like leaves, which are specialized for photosynthesis.
• A leaf is made of:
  • Dermal tissue: Covers the outer surface.
  • Ground tissue: Produces food through photosynthesis and is tightly packed on the top half of the leaf.
  • Vascular tissue: Moves food and water throughout the leaf and plant.

How are organs organized in the body?

Organs are important for an organism’s survival and work together to perform important functions.

Organ Systems

• Organs usually do not work alone; they form organ systems, which are groups of organs working together to complete tasks.
• For example, the human digestive system includes organs like the stomach, small intestine, liver, and large intestine, which work together to break down food and take nutrients into the body.
• Plants have two major organ systems:
  • Shoot system: Includes leaves, stems, and flowers; transports food and water.
  • Root system: Anchors the plant and takes in water and nutrients.

How are organ systems organized in the body?

• In multicellular organisms, similar cells form tissues.
• Tissues are organized into organs.
• Organs are organized into organ systems.
• Organ systems work together to keep the organism functioning.

Organisms

• Multicellular organisms have many organ systems that work together to perform all the jobs needed for survival.
• In plants, the shoot system transports water from the roots to the leaves and stems, which need water to live.
• In humans, organ systems depend on each other. For example:
  • Muscle tissue in the stomach needs oxygen to survive.
  • The stomach works with the respiratory and circulatory systems to get oxygen.

A Closer Look: Organ Donation

• Every 10 minutes, someone in the United States is added to the national transplant waiting list for an organ.
• About 120,000 people are currently on the transplant waiting list.
• Only 54% of Americans are registered as organ donors.
• An organ donor agrees to donate their organs after death to help someone in need.
• Some organs, like kidneys or livers, can be donated by living people, and both the donor and recipient can live healthy lives afterward.
• The kidney is the most commonly donated organ from a living donor.
• People waiting for a kidney transplant need dialysis, a process that removes waste from the blood artificially.