Science Study Guide - Unicellular & Multicellular Organisms - PDF

Science study guide Unicellular organisms are tiny organisms made up of just one cell, and they can either help or harm the body. ​ 1.​ Helpful unicellular organisms: Some unicellular organisms, like the good bacteria in your gut, help your body by breaking down food, helping with digest...

Science study guide Unicellular organisms are tiny organisms made up of just one cell, and they can either help or harm the body. ​ 1.​ Helpful unicellular organisms: Some unicellular organisms, like the good bacteria in your gut, help your body by breaking down food, helping with digestion, and keeping harmful bacteria from taking over. These “good” microorganisms are important for keeping your digestive system healthy and your immune system strong. ​ 2.​ Harmful unicellular organisms: On the other hand, some unicellular organisms, like certain bacteria and parasites, can cause infections and diseases. For example, harmful bacteria can cause infections like food poisoning, and parasites can make you sick by living inside your body. These harmful unicellular organisms invade the body, multiply, and damage tissues, which can make you feel sick. So, unicellular organisms can be helpful when they support your body, but they can also be harmful when they cause infections or diseases. The balance between good and bad microorganisms is important for staying healthy. A unicellular organism is a living organism that consists of only one cell. This single cell performs all the necessary functions for survival, such as growth, reproduction, and metabolism. Examples of unicellular organisms include: ​ ​ Bacteria (e.g., Escherichia coli) ​ ​ Protozoa (e.g., Amoeba, Paramecium) ​ ​ Some algae (e.g., Chlamydomonas) ​ ​ Some fungi (e.g., Yeast) Unlike multicellular organisms, where different cells have specialized functions, unicellular organisms rely entirely on their single cell to carry out all life processes. A multicellular organism is a living organism made up of more than one cell. These cells are specialized and work together to perform different functions, such as digestion, movement, and respiration. Examples of Multicellular Organisms: ​ ​ Humans and animals (e.g., dogs, birds, fish) ​ ​ Plants (e.g., trees, flowers, grass) ​ ​ Fungi (e.g., mushrooms) Multicellular organisms have organized structures, such as tissues, organs, and organ systems, which allow them to perform complex functions that unicellular organisms cannot. Yes, humans and earthworms both rely on gas exchange to breathe, but they do it in different ways. Interestingly, there is a connection between them in terms of oxygen and carbon dioxide exchange in the environment. How Humans Breathe (Gas Exchange in Humans) ​ ​ Humans breathe using their lungs. ​ ​ They inhale oxygen (O₂) from the air, which enters the lungs and diffuses into the bloodstream. ​ ​ The oxygen is transported to cells, where it is used for energy production. ​ ​ As a byproduct, cells produce carbon dioxide (CO₂), which is carried back to the lungs and exhaled. How Earthworms Breathe (Gas Exchange in Earthworms) ​ ​ Earthworms do not have lungs; they breathe through their moist skin. ​ ​ Oxygen from the air dissolves in the mucus on their skin and diffuses directly into their bloodstream. ​ ​ Similarly, carbon dioxide from their bodies diffuses out through the skin into the air. Gas Exchange Between Humans and Earthworms ​ ​ Humans exhale carbon dioxide, which is released into the air. ​ ​ Plants absorb this CO₂ during photosynthesis and release oxygen back into the air. ​ ​ Earthworms, living in the soil, absorb this oxygen through their skin for respiration. ​ ​ They then release CO₂, which contributes to the cycle. This shows how humans, earthworms, and even plants are interconnected in the oxygen-carbon dioxide cycle, helping maintain balance in nature. Invertebrate is animal without a backbone Vertebrate is a animal with a backbone Fungi - organisms that usually obtain nutrients from dead or decaying matter and cannot carry out photosynthesis; nutrients are usually absorbed. Protist - an organism that is neither plant nor animal, but shares many of the same characteristics of both; usually unicellular, but can be multicellular. Bacteria - the most basic of all unicellular organisms; lacks a nucleus. Movement - a change in the shape or figure of all or part of an organism; a characteristic of all living things. Locomotion - movement that takes an object from one place in its environment to another; a characteristic of animals, animal-like protists, and some bacteria, but not plants or fungi The five main organs in the human body—brain, heart, lungs, liver, and kidneys—work together to keep the body functioning properly. Each organ belongs to a specific system but interacts with others to maintain homeostasis (a stable internal environment). 1. Brain (Nervous System) – The Control Center ​ ​ Sends and receives signals to regulate body functions. ​ ​ Controls movement, breathing, heartbeat, and digestion by communicating with other organs. ​ ​ Works closely with the heart and lungs to ensure oxygen reaches brain cells. Example: The brain tells the heart to beat faster during exercise to pump more oxygen to muscles. 2. Heart (Circulatory System) – The Pump ​ ​ Pumps oxygen-rich blood from the lungs to the body. ​ ​ Delivers nutrients and oxygen to cells and removes waste. ​ ​ Works closely with the lungs, brain, and kidneys to regulate blood flow and oxygen levels. Example: When blood pressure drops, the heart beats faster to circulate more oxygen. 3. Lungs (Respiratory System) – Oxygen Supply ​ ​ Take in oxygen and remove carbon dioxide from the body. ​ ​ Oxygen is transferred to the bloodstream, which the heart pumps to the brain and body. ​ ​ Works closely with the heart to ensure cells get enough oxygen. Example: The lungs increase breathing rate during exercise to provide more oxygen to the blood. 4. Liver (Digestive System & Detoxification) – The Filter ​ ​ Processes nutrients from food and stores energy. ​ ​ Removes toxins from the blood. ​ ​ Works closely with the heart and kidneys to clean the blood and regulate sugar levels. Example: After eating, the liver stores excess sugar and releases it when needed for energy. 5. Kidneys (Excretory System) – Waste Removal ​ ​ Filter blood to remove waste and extra fluids, producing urine. ​ ​ Help regulate blood pressure and water balance. ​ ​ Work closely with the heart and liver to maintain a clean, balanced bloodstream. Example: If the body is dehydrated, the kidneys retain more water instead of producing urine. How They Work Together (Example Scenario) Imagine you run a race: ​ 1.​ Your brain signals your muscles to move and tells your heart to pump faster. ​ 2.​ Your heart increases blood flow to deliver more oxygen. ​ 3.​ Your lungs work harder to bring in more oxygen. ​ 4.​ Your liver releases stored energy to fuel your muscles. ​ 5.​ Your kidneys filter out waste and help maintain fluid balance. All five organs constantly communicate to keep the body functioning