Blood. Red cells

1. The average adult has five litres of blood pumping around their body. About 20 per cent of this blood is in the heart and arteries, whooshing out through the aorta at 45 centimetres per second for a person at rest. It reaches lows of just 0.5 millimetres per second as it branches out into the maze of tiny capillaries which deliver oxygen to cells, tissues and organs.

2. The blood picks up speed again to around 25 centimetres per second as it returns to the heart in larger veins. The average speed of blood in the body is 28 centimetres per second, which equals about 17,000 kilometres in a week. The reality is far more complicated as blood pressure and heart rate (linked to how active you are, among other factors) affect blood velocity dramatically.

3. Blood is red because it contains iron, bound up in a ring-like chemical structure called porphyrin within haemoglobin – the protein responsible for carrying oxygen around the body. Haemoglobin is crammed into our red blood cells, making them red too. Red blood cells are round with a flattish, indented center, like doughnuts without a hole. They play an important role in your health, remove carbon dioxide from your body, transporting it to the lungs for you to exhale. Red blood cells are made inside your bones, in the bone marrow (костный мозг). They typically live for about 120 days, and then they die.

Red blood cells, white blood cells and platelets (тромбоциты) are the key components of blood, floating in clear plasma, but the sheer volume of red blood cells gives blood a red colour overall. 

4. Oxygen-rich blood is a bright red, whereas deoxygenated blood is a darker brownish red. The veins in your wrists (запястие) may appear blue but they are red too – the blue colour is the result of the way light travels through your skin. While all vertebrates (позвоночные) share the same colour blood, blue blood does exist – eg horseshoe crabs have no haemoglobin, having opted (выбрав) instead for haemocyanin, a copper-based (содержащий медь) protein.

Infectious disease

1. Infectious disease – those spread by contact with infected people or animals, through airborne inhalation, or by water or food – are still threads to us today. The influenza virus for example infects a staggering 5 million people worldwide every single year, travelling from person to person in airborne droplets, and causing chills, fever, sore throat, runny nose, headaches and muscle pain.

2. The flu virus changes gradually by a process known as antigenic drift. As the virus replicates, single nucleotide errors occur in the viral genome, causing minute changes to the proteins that coat the outside of the virus. The immune system recognizes these proteins to detect and destroy the infection, so as they change, the ability of the body to recognize the virus decreases, preventing people from building up immunity. Not only does the virus make continual, subtle changes to its genome and proteins, but it also occasionally develops huge mutations.

3. Spanish Flu is a truly global pandemic, some believe that this influenza virus, which emerged in 1918, killed as many as 40-50 million people around the world. The Black Death is an infamous bubonic plague outbreak swept across Asia into Europe with a total death toll of roughly 100 million.

4. Flu virus can definitely cause a pandemic in the future. As for other diseases, it is hard to predict. The human immunodeficiency virus has raged since the early-Eighties. This pandemic has claimed around 25 million lives. Approximately 34 million people currently have HIV across the globe. Could a pandemic end humanity? It could. But there are medical and allied sciences like epidemiology and modelling are so strong now. It is unlikely a pandemic would wipe out humanity, but it could cause huge damage, particularly in some areas of the world with weak health infrastructure.

Introduction to the Animal Kingdom

Vocabulary list

lack - to not have something, or not have enough of something: An animal cell lacks cell walls.

share - to have the same interest/opinion, etc as someone else: All plants share certain characteristics.

enable - to make someone able to do something, or to make something possible: Many body functions enable animals to maintain homeostasis.

vertebral column / backbone - a ​spine, the line of bones down the centre of animal’s back

vertebrate - an ​animal that has a ​spine /invertebrate - an ​animal with no ​spine: Invertebrates, such as ​worms, are the ​main ​diet of these ​water ​birds.

bilateral symmetry - the fact of the two halves of something on either side of a particular line being exactly the same / radial symmetry - the condition of having similar parts regularly arranged around a central axis

homeostasis - internal conditions remain stable and relatively constant.

body cavity - any fluid-filled space in a multicellular organism other than those of vessels.

All members of kingdom Animalia share certain characteristics. Animals are multicellular, eukaryotic heterotrophs whose cells lack cell walls. The bodies of most animals contain tissues. Over 95 percent of all animal species are often grouped in a single, informal category: invertebrates. Invertebrates are animals that have no backbone, or vertebral column. The other 5 percent of animals are called vertebrates, because they have a backbone.

Animals carry out the following essential functions: feeding, respiration, circulation, excretion, response, movement, and reproduction. The study of the functions of organisms is called physiology. The structure, or anatomy, of an animal’s body enables it to carry out physiological functions. Many body functions help animals maintain homeostasis. Homeostasis is often maintained by internal feedback mechanisms. Most of these mechanisms involve feedback inhibition, in which the product or result of a process stops or limits the process. Complex animals tend to have high levels of cell specialization and internal body organization, bilateral symmetry, a front end or head with sense organs, and a body cavity.

Answer the questions:

What is an animal?

What animals can be called invertebrates?

What essential physiological functions do animals carry out?

 What type of symmetry do vertebrates have?

Labeling Diagrams

Use the following words to label the structures of the animal below: nerve, cord, notochord, pharyngeal pouches, and tail. Then, complete the sentence.

 

5. The animal diagrammed above is an example of a (an) _______________ .

The Chordates

Vocabulary list

nerve cord - the single, hollow, fluid-filled, dorsal tract of nervous tissue

dorsal – that takes place on one’s back

pharyngeal pouches – “throat pockets” that are inside the body

gill slits - individual openings to gills outside the body

gill - a respiratory organ found in many aquatic organisms

rod - a thin, straight pole

tunicates (sea squirts) - creatures, looking like a vase with two openings

lancelets (technically, cephalochordates) - creatures, looking much more like the fish

A chordate is an animal that has a hollow nerve cord, a notochord,pharyngeal pouches, and a tail. These characteristics need not be present during the entire life cycle of a chordate animal.

The hollow nerve cord runs along the back of the body. Nerves branch from it and connect to organs and muscles. The notochord is a rod that runs just below the nerve cord. It gives support.

Pharyngeal pouches are paired structures in the throat. In some chordates, they develop into gills.

Most chordates are vertebrates. Vertebrates have a backbone made of segments called vertebrae. The backbone replaces the notochord. The backbone gives support and protects the spinal cord. It also gives the muscles a place to attach.

Two groups of chordates do not have backbones. Tunicates are filter feeders that live in the ocean. Adult tunicates have neither a notochord nor a tail. Larval tunicates have the chordate characteristics.

The other group of chordates without a backbone is the lancelet. Lancelets are small, fishlike animals. Adult lancelets have all four chordate characteristics. They also have a definite head region.

Answer the questions:

What is a chordate?

Does a chordate animal present all chordate characteristics during its entire life cycle?

What tissue forms the nerve cord?

What organ can pharyngeal pouches in some chordates develop into?

What does a spinal cord protect?