Biology Paper 2, Topic 6 "Inheritance, variation and selection" Know that some disorders are inherited. These disorders are caused by the inheritance of certain alleles. Polydactyly having extra fingers or toes is caused by a dominant allele. Cystic fibrosis a disorder of cell membranes is caused by a recessive allele.
Key points Humans—and other complex multicellular organisms—have systems of organs that work together, carrying out processes that keep us alive. The body has levels of organization that build on each other. Cells make up tissues, tissues make up organs, and organs make up organ systems.
The function of an organ system depends on the integrated activity of its organs. For instance, digestive system organs cooperate to process food. The survival of the organism depends on the integrated activity of all the organ systems, often coordinated by the endocrine and nervous systems. Introduction If you were a single-celled organism and you lived in a nutrient-rich place, staying alive would be pretty straightforward.
For instance, if you were an amoeba living in a pond, you could absorb nutrients straight from your environment. The oxygen you would need for metabolism could diffuse in across your cell membrane, and carbon dioxide and other wastes could diffuse out.
When the time came to reproduce, you could just divide yourself in two! How, then, does the body nourish its cells and keep itself running?
Let's take a closer look at how the organization of your amazing body makes this possible. Multicellular organisms need specialized systems Most cells in large multicellular organisms don't directly exchange substances like nutrients and wastes with the external environment, instead, they are surrounded by an internal environment of extracellular fluid—literally, fluid outside of cells.
The cells get oxygen Fight or flight and homeostasis nutrients from this extracellular fluid and release waste products into it. Humans and other complex organisms have specialized systems that maintain the internal environment, keeping it steady and able to provide for the needs of the cells.
Different systems of the body carry out different functions.
For example, your digestive system is responsible for taking in and processing food, while your respiratory system—working with your circulatory system—is responsible for taking up oxygen and getting rid of carbon dioxide.
The muscular and skeletal systems are crucial for movement; the reproductive system handles reproduction; and the excretory system gets rid of metabolic waste. Because of their specialization, these different systems are dependent on each other. The cells that make up the digestive, muscular, skeletal, reproductive, and excretory systems all need oxygen from the respiratory system to function, and the cells of the respiratory system—as well as all the other systems—need nutrients and must get rid of metabolic wastes.
All the systems of the body work together to keep an organism up and running. Overview of body organization All living organisms are made up of one or more cells.
Unicellular organisms, like amoebas, consist of only a single cell. Multicellular organisms, like people, are made up of many cells. Cells are considered the fundamental units of life. The cells in complex multicellular organisms like people are organized into tissues, groups of similar cells that work together on a specific task.
Organs are structures made up of two or more tissues organized to carry out a particular function, and groups of organs with related functions make up the different organ systems. From left to right: For instance, the cells in the small intestine that absorb nutrients look very different from the muscle cells needed for body movement.
The structure of the heart reflects its job of pumping blood throughout the body, while the structure of the lungs maximizes the efficiency with which they can take up oxygen and release carbon dioxide.
Types of tissues As we saw above, every organ is made up of two or more tissues, groups of similar cells that work together to perform a specific task. Humans—and other large multicellular animals—are made up of four basic tissue types: The four types of tissues are exemplified in nervous tissue, stratified squamous epithelial tissue, cardiac muscle tissue, and connective tissue in small intestine.
For instance, the outer layer of your skin is an epithelial tissue, and so is the lining of your small intestine. Epithelial cells are polarized, meaning that they have a top and a bottom side. The apical, top, side of an epithelial cell faces the inside of a cavity or the outside of a structure and is usually exposed to fluid or air.
The basal, bottom, side faces the underlying cells. For instance, the apical sides of intestinal cells have finger-like structures that increase surface area for absorbing nutrients. Image showing three cells lining the small intestine.
Each cell contains a nucleus and is surrounded by a plasma membrane. The tops of the cells have microvilli that face the cavity from which substances will be absorbed.
Often, the cells are joined by specialized junctions that hold them tightly together to reduce leaks. Connective tissue Connective tissue consists of cells suspended in an extracellular matrix.
In most cases, the matrix is made up of protein fibers like collagen and fibrin in a solid, liquid, or jellylike ground substance. Connective tissue supports and, as the name suggests, connects other tissues.While fight or flight indicates a stressful response of the body to perceived danger, homeostasis is the body's tendency to preserve the stable conditions necessary for life and health in the midst of the challenges of change.
Most people have heard of the “fight or flight” response of the nervous system, the way in which the body reacts to stress or danger. Many, however, have never heard of the “rest and digest” response. Walter Cannon is responsible for coining and researching some key concepts about stress such as "fight or flight" and "homeostasis".
His scientific research demonstrates and explores the interrelationship of stress & change, mind & body. Adrenaline, also known as adrenalin or epinephrine, is a hormone, neurotransmitter, and medication.
Epinephrine is normally produced by both the adrenal glands and certain neurons. It plays an important role in the fight-or-flight response by increasing blood flow to muscles, output of the heart, pupil dilation response, and blood sugar level.
It does this by binding to alpha and beta receptors. If you were a single-celled organism and you lived in a nutrient-rich place, staying alive would be pretty straightforward. For instance, if you were an amoeba living in a pond, you could absorb nutrients straight from your environment.
Pilot fatigue is a constant threat to all aircrew. There are particular risk factors for those flying high-performance fighter platforms. Flying high-G sorties is physically exhausting.