#116 The development of the fetus

Credit: thomasreynoldsblog

The blastula develops into an embryo and some of the cells form a placenta, linking the embryo with the uterus lining. Organs such as the heart develops and, after 8 weeks, the embryo is called a fetus.

#115 Formation of the fetus - fertilisation, implantation

After sexual intercourse, sperms swim through the cervix and the uterus into the oviducts, where they meet an egg. One sperm may fertilise the egg to produce a zygote. 

#114 Menstrual cycle

The menstrual cycle in women is a recurring process in which the lining of the uterus is prepared for pregnancy, and if pregnancy does not happen, the lining is shed at menstruation. The cycle lasts about 28 days.

#113 Reproduction in humans - Reproductive system

Reproduction in humans is when the male gamete (sperm) fuses together with the female gamete (ovum/egg).

At first, it is just one single cell, which duplicates over and over until after 9 months…… TA-Dahh! - A baby is born!

#112 Growth and development

Growth - permanent increase in size and dry mass, by an increase in cell number or cell size or both.

Development - increase in complexity 

#111 Self-pollination and cross-pollination

Credit: TutorVista

Self-pollination - transfer of pollen from the anther to the stigma of the same flower, or to another flower of the same plant.

Cross-pollination - transfer of pollen from the anther of a flower to the stigma of a flower on a different plant of the same species.

#110 Seed dispersal

Nutmeg is dispersed by birds.
Photo credit: russolab.unl.edu

The flowers produce seeds which can be dispersed by the wind or other animals, providing a means of colonising new areas.

#109 Formation of seed, conditions affecting germination

The fertilised ovule divides by mitosis to form a seed containing the embryo plant and food stores called cotyledons.

#108 Structure and functions of a flower

You need to be able to describe the structure and functions of a named dicotyledonous (two seed leaves) flower.

#107 Reproduction in plants - agents of pollination

Reproduction in flowering plants may occur both sexually or asexually.

Pollination can take place with the help of agents: wind or insects.

#106. Types of reproduction

Reproduction is the process that makes more of the same kind of an organism.

There are 2 types of reproduction: asexual and sexual.

11 Homeostasis and Drugs pdf

# 105 Summary of homeostasis, excretion, drugs

Homeostasis is the maintenance of a constant internal environment. It is achieved using negative feedback.

#104 Drugs: antibiotics, heroin, alcohol

Drug is any substance taken into the body that modifies or affects chemical reactions in the body. Drug used in medical care, or to relieve mild pain, are very helpful to us. However, some people misuse drugs, so that they cause harm to themselves and to others around them. 

#103 Negative feed back in homeostasis

Temperature and glucose blood levels regulation involve negative feedback: 

- a change from normal conditions (body temperature, blood glucose levels…) 

- triggers a sensor, 

- stimulates a response in an effector.

#102 Control of blood glucose content

The control of glucose concentration in the blood is a very important part of homeostasis. 

Two hormones insulin and glucagon control blood glucose levels. 

Both hormones are secreted by the pancreas and are transported to the liver in the bloodstream.

#101 Homeostasis

Homeostasis is the maintenance of a constant internal environment, which is vital for an organism to stay healthy. Fluctuations in temperature, water levels and nutrient concentrations … could lead to death.

10. Excrestion pdf

# 100 Dialysis and its application in kidney machines

The usual treatment for a person with kidney failure is to have several sessions a week using a dialysis unit (a kidney machine), to maintain the glucose and protein concentration in blood diffusion of urea from blood to dialysis fluid.  

# 99 Urea formation, breakdown of alcohol & drugs in liver

Photo credit: James X - Biology Blog

Surplus amino acids in the bloodstream cannot be stored. They are removed by the liver and broken down into the urea (which is the nitrogen-containing part of the amino acid) and a sugar residue, which can be respired to release energy. The breakdown of amino acids is called deamination.

# 98 Function of the kidney - filtration and reabsorption

The function of the kidney is to filter blood, removing urea and excess H₂O, reabsorbing glucose, some H₂O and some mineral salts. 

#97 Structure of the kidney, the nephron

 Excretion is the removal  from organisms of toxic materials, the waste products of metabolism and substances in excess of requirements (carbon  dioxide, urea, salts…).

09. Coordination and Response pdf

#96 Summary of coordination and response

All organisms are able to sense changes in their environment, called stimuli, and respond to them. The part of the body that senses the stimulus is a receptor, and the part that responds is an effector.

#95 Control of plant growth by auxins, weedkillers

Auxins are plant growth substances, produced by the shoot and root tips of growing plants.

- Auxins in the shoot → stimulate cell growth, by the absorption of water.

- Auxins in the root → slow down the cell growth.

#94 Coordination in plants – tropism

Tropism are responses by part of a plant toward of away from a stimulus coming from one direction.

The movement is always a growth movement. 

#93 Voluntary and involuntary actions

Knee jerk is an involuntary reflex. 

Two types of action controlled by the human nervous system are: voluntary and involuntary actions. The peripheral nerves transmit both of them.  

#92 Use of hormones in food production

 Farmer sometimes use hormones to make their animals grow faster, or to produce more of a particular product. One hormone used in this way is called bovine somatotropin, or BST.

#91 Hormones, role of adrenaline

Credit:biologie.uni-hamburg.de

Hormone is a chemical substance, secreted by endocrine gland, carried by the blood, which alters the activity of one or more  specific  target organs and is then destroyed by the liver.

# 90 Accommodation - focusing on objects far and near

The amount of focusing needed by the lens depends on the distance of the object being viewed – light from near objects requires a more convex lens than light from a distant objects. 

#89 Structure and function of the eye, rods and cones

You need to be able to label parts of the eye on diagrams. 

#88 Effectors, biceps and triceps

Effectors are muscles or glands which respond when they receive impulses from motor neurones. Examples of effectors are the biceps and triceps muscles in the arm. 

#87 Simple reflex arc

A reflex action is an automatic response to a stimulus. 

A reflex arc describes the pathway of an electrical impulse in response to a stimulus.

# 86 The human nervous system

The human nervous system is made up of two parts: 

• Central nervous system (CNS) - brain and spinal cord: role of coordination
• Peripheral nervous system - nerves: connect all parts of the body to the CNS. 

Together, they coordinate and regulate body functions.