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Open and Closed Circulatory Systems: Differences, Examples and Adaptations

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The circulatory system is responsible for the movement of important substances within the bodies of living organisms. These substances include oxygen, nutrients, hormones and metabolic wastes. However, circulation does not occur in exactly the same way in all organisms. Depending on how the circulatory fluid moves within the body, circulatory systems are generally classified as open circulatory systems and closed circulatory systems . To better understand the general patterns of circulation found in different organisms, you may also read our previous article on Types of Circulation and Their Organisms . What Is an Open Circulatory System? An open circulatory system is a type of circulatory system in which the circulatory fluid is not always enclosed within blood vessels. The heart pumps the circulatory fluid into body spaces called sinuses or haemocoels . The fluid then comes into direct contact with the tissues and organs before eventually returning to the heart. In many animals wi...
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Why Do We Yawn? The Surprising Science Behind Yawning

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Yawning is one of the most common human behaviours, yet many people do not know exactly why it happens. A yawn usually involves opening the mouth widely, taking in a deep breath and then slowly breathing out. We yawn when we are tired, sleepy or bored, but yawning can also occur when we have just woken up, feel stressed or even when we see another person yawn. But why exactly do human beings yawn?                                                      What Happens During a Yawn? When a person yawns, several muscles in the face and jaw become active. The mouth opens widely, the chest expands and a deep inhalation may occur. This is usually followed by a slower exhalation. Yawning is an involuntary action, meaning that it often happens without conscious planning. Although we can sometimes suppress a yawn, the urge to yawn may become ...
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Types of Circulation in Organisms (With Examples from Different Phyla and Classes)

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Photo Credit: Ahmad Coaching Circulation refers to the movement of fluids, such as blood or haemolymph, within an organism’s body. It helps in the transport of nutrients, gases, and waste products. In living organisms, there are different types of circulation depending on their level of organisation and body structure. The two major types of circulation in animals are: Open circulatory system Closed circulatory system Open Circulatory System In an open circulatory system, the circulatory fluid (called haemolymph) is not always contained within blood vessels. Instead, it flows freely within body cavities and comes into direct contact with body tissues. Characteristics: Blood is not fully enclosed in vessels. Haemolymph bathes organs directly. Pressure is low and circulation is slow Organisms with Open Circulatory System This system is mainly found in the Phylum Arthropoda and some members of Phylum   Mollusca . Examples: Phylum Arthropoda Insects (e.g. grasshopper, cockroach, butte...
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The Human Circulatory System: Structure and Functions Explained Simply

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THE CIRCULATORY SYSTEM Photo Credit: Olga The circulatory system is one of the most important systems in the human body. It is responsible for the movement of blood, nutrients absorbed during digestion, oxygen, hormones, and waste products throughout the body. Without this system, the body would not be able to function properly. The circulatory system consists of three main parts, namely: The heart The blood vessels The blood Each of these parts works together to ensure continuous circulation. The Heart The heart is a muscular organ that acts as a pump. It keeps blood moving around the body by contracting and relaxing continuously. It has four chambers, which are: - Right atrium - Right ventricle - Left atrium - Left ventricle The right side of the heart handles deoxygenated blood, while the left side handles oxygenated blood. Read more: The Human Heart: Structure and Functions The Blood Vessels Blood vessels are tubes that transport blood throughout the body. There are three main type...
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The Human Heart: Structure and Functions Explained Simply

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The human heart is one of the most important organs in the body. It is responsible for pumping blood to all parts of the body, supplying oxygen and nutrients necessary for survival. Although many students find the heart difficult to understand, it can be explained in a simple and clear manner. So, the heart's a muscular organ located in the chest, slightly to the left side. It's about the size of a clenched fist and is protected by the rib cage. The main gig of the heart is to pump blood continuously throughout the body. This process is essential for transporting oxygen, nutrients, hormones, and waste products. Now, let's get into the nitty-gritty – The human heart consists of four chambers, namely: Right atrium Right ventricle Left atrium Left ventricle  DIAGRAM OF THE MAMMALIAN HEART  Photo Credit: Georgia Tech Biological Sciences Each chamber has a specific role in the movement of blood. The right atrium receives deoxygenated blood from the body. This blood then flows in...
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How to Answer Biology Questions Correctly in Exams

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1. Understand the Question - Keywords are crucial: Words like "define", "explain", "describe", "list" dictate how you answer. Make sure you know what each instruction means.     - Define: Give a clear, concise meaning of a term or concept.     - Explain: Provide reasons, mechanisms, or processes behind something.     - Describe: Detail the process, structure, or features of something.     - List: Enumerate points briefly, often without much explanation. 2. Be Clear and Direct - Get straight to the point: Avoid lengthy introductions or info that's not relevant to the question. Examiners want answers, not stories. - Focus on what's asked: If the question is about liver functions, don't write everything about the liver. Stick to the functions. - Example: "Functions of the liver include:     - Bile production     - Detoxification     - Glycogen storage" 3. Use Biological Terms Correctly - Use precise vocabulary: Shows you...
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Common Mistakes Students Make in Exams and How to Avoid Them

Examinations are a major part of every student's academic journey. However, many students fail not because they are not intelligent, but because they make avoidable mistakes during exams. These mistakes often reduce their chances of success, even when they have studied well. Understanding these common errors and learning how to avoid them can greatly improve performance. Top Exam Blunders 1. Poor Preparation : Some students wait until the last minute to start reading, leading to confusion and stress. To avoid this, you should study regularly and revise their notes frequently. 2. Not Reading Instructions Carefully : Many students lose marks because they fail to follow instructions. For example, a question may require "Explain" but the student only "Lists" points. 3. Poor Time Management : Spending too much time on one question can lead to rushed or unanswered questions. Allocate time according to the number of questions and marks. 4. Unclear Answers : Poor presen...
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