2.75 Urine

2.74 ADH.

2.73 Glucose reabsorption

2.72 Water re-absorption.

2.71 Ultrafiltration

2.70 Nephron Structure

1.68 Urinary System

The urinary system includes

1.       Kidneys : excretion, filtration and osmoregulation

2.       Ureter : (one for each kidney) delivers urine to bladder

3.       Bladder : (One bladder for both ureters) delivers urine to urethra

4.       Urethra

2.68 Excretion

a)      The role of the kidney in the excretion of urea which is made from nitrogen in the form of amino acids, excess amounts can be toxic to the body therefore needs to be excreted.

Amino acids are broken down in to urea in the liver. Urea then circulates with blood into the kidneys which then filters the blood from the urea. Water is then added to urea to create urine and is then transferred to the bladder ready for excretion.

b)      Osmoregulation

Osmo : osmosis

Regulation : to control

Osmoregulation : to control the transfer of liquids

It is the role of the kidney to control the composition of the blood; maintaining control of excess water and salts in the blood by excretion, which in turn keeps the tissue fluid isotonic to the cell cytoplasm maintaining functions of cells.

2.67 Excretion

a) the origin of carbon dioxide and oxygen as waste products of metabolism and their loss from the stomata of a leaf

b) major organs of excretion

3.34 Causes of Mutation

The incidence of mutations  can be increased by exposure to ionising radiation (gamma rays, X-rays and ultraviolet rays) and some chemical mutagens (tabbaco)

1.       Radiation – such as the sun (UV-B)   which can cause skin cancer.

2.       Chemicals can also cause mutations such as the effect of tar in tabbaco causing mutations in the base sequence producing new alleles. Chemicals that cause mutations are called mutagens. Chemicals which cause mutations and cancer are called carcinogens.

3.32 Types of mutation

The mutation in a gene creating new alleles can be, beneficial, harmful or nuetral ( neither positive or negative)

An example of a beneficial mutation can be improving the efficiency of an enzyme.

An example of a harmful mutation can be production of a enzyme that doesn’t work.

An example of a nuetral mutation can be production of  that has no particular effect on an idividual, though in the long run it may due to environmental changes.

3.33  Antibiotic Resistance

How resistance to antibiotics can increase in bacterial population.

3.30 Mutation

The base sequence in which the letters are arranged constitutes the gene, the form of the gene is called the allele.

The base sequence of the DNA can be changed as shown in the diagram, producing a new allele which can produce an entirely different protien affecting the phenotype this is called mutation and this is also how the variation in the phenotypes occur.

3.29 Species variation

Variation is the differences that can be seen in the phenotype of individuals.

Every individual has a phenotype which depends on that individuals genotype which can be influenced by that particular persons living environment.

Variation in a population are the differences in the phenotypes of each individual, this is caused by variation in the species genotype and changes in the environment they live in.

1)      Variation caused by genes (discontinueos)

2)      A combination of variation caused by genes and environment ( continueos)

3)      Variation caused by environment

The third type of variation in population can be purely to do with environmental variation and has nothing to do with genetic charateristics, an example of this is the home language that an individual speaks. This cannot be inherited.

3.21 Genetic Probabilities

a) Predicting the probabilities of outcomes from monohybrid crosses

-the chance of offspring from one type of gene

Parents : red petal flower x white petal flower ( red is dominant )

Genotype : RR x rr

Through meiosis all genotypes os the offspring half of each of the parent alleles, which in this case is R and r.

Producing four heterozygotes

Genotype of offspring is all Rr

Phenotype of offspring is all red

When a homozygous red petaled flower is crossed with a homozygous white petaled flower the genotype of the offspring produced is Rr therefore the phenotype has a probability of 100% red.

b) crossing F1 offsprings

Parent phenotype : red x red

Parent genotype : Rr x Rr

Both Parents are heterozygotes

Through Meiosis all genotypes of the offspring will include half of each parents alleles.

 

Genotypes of offspring:                      RR   :  2Rr  : rr

Phenotype ratio of offspring(F2):     Red : Red : White    

                                                                         1   :   2    :    1

                                                                         3         :          1

                                                                         75%    :       25%

3.20a and b Pedigree diagrams

3.21b Genetic Probabilities

3.21a Genetic Probabilities

3.18c Codominance

codominance is when both genotypes contribute to the phenotype.

e.g. 

allele key :

blue flower : BB

white flower : WW

BB + WW = BW(orange flower)

3.19 a and b

3.18 a and b

3.12 amniotic fluid

the developing embryo is protected by the amniotic fluid 

within the uterus, surrounding the embryo is a fluid called the amniotic fluid

one of the functions of the amniotic fluid is to protect the embryo, this is possible because the fluid is made largely of water which cannot be compressed

the fluid absorbs any pressure on the outside wall of the uterus preventing damage to the unborn child 

(it is hard to create great force within water) 

3.11 PLACENTA

the role of the placenta in the nutrition of the developing embryo

the placenta structure includes :

the umbilical cord, contains the umbilical arteries and the umbilical vein which connects the embryo to the placenta

the placenta grows out of the developing embryo not the mother, the blood vessels in the cord belongs to the baby

the placenta grows into the wall of the uterus

glucose, amino acids and fats in the mothers blood vessels-which is gained from food-travels into the wall of the uterus, and there the molecules will cross into the child's blood via the placenta.

the large surface area and thin barrier between the mother and the child makes this efficient.

nutrients that the child receives are taken from the mother

the child also produces molecules which exchanges into the maternal blood including CO2 and urea

3.9A The Male Reproductive System

the structure and functions of the male reproductive system

the male reproductive system includes the following structures:

BLADDER : used to store urine

TESTIS : used to carry out meiosis, which produces gamete known as sperm cells

EPIDIDYMIS : used to store sperm cells

VAS DEFERENS : used to carry sperm cells to the penis during sexual stimulation

PROSTATE : 20-30% of the volume of semen, it is known to contain sugars and is also alkaline which nuetralises the acidic secretions of the vagina

SEMINAL VESICLES : 70% of the semen which contains sugars and is alkaline.

URETHRA : joins left and right testis and the left and right vas deferens, it also takes the semen down the penis. it is also an exit to urine which is stored in the bladder

PENIS : carries sperm cells into the vagina during sexual intercourse 

3.24c stages of mitosis

the nucleus of the cell contains the chromosomes, during the resting stage of the cell cycle known as the interphase the chromosomes are copied in  a process known as DNA replication, this process creates two copies of each chromosome which are held together by a structure known as the centromere.

stages of mitosis includes ::
the nucleus membrane breaks down in the process of cell division, called prophase. chromosomes become visible as a pair of chromatids.
a network of of protein molecules appear called spindles the chromosome will move towards the spindle during the late prophase and will move finally join onto a spindle fibre at the centromere known as the metaphase, in this phase the chromosomes are in the middle arranged across the equator of the cell.
the next phase is the amaphase where the spindle fibre shortens so the chromatids gets pulled apart to opposite poles of the cell.
telophase is the end of mitosis where the nucleus begins to reform around the chromosomes at the end of the phase two nuclei are formed at opposite ends of the cell.
cytokinesis is not considered a stage of mitosis but it is where the cell splits to form two cells, each with one chromosome in, identical to the parental cell.

3.24a mitosis

mitosis, a form of cell division which results in growth because of a n increase in the number of cells.

diploid(2n) is the number of chromosomes in a nucleus.
e.g. for humans 2n=46 ( the diploid number for humans is 46)

In the process of the mitosis a cell will divide into two cells each with a diploid nucleus, they can be described as identical or daughter cells. They are 'identical' because they have the same number of chromosomes and the same set of chromosomes.

3.16 structure of the DNA molecule

3.16 a DNA molecule as two strands coiled to form a double helix, the strands being linked by a series of paired bases: adenine (A) with thymine (T) and the cytosine (C) with guanine (G)

the two strands of helixes are called the ‘sugar-phosphate backbone’ they are linked together by pairs of four different types of bases (two pairs).

the order of the bases on one side of the double helix, are what is called the gene. 

3.15 the gene is a section of a molecule of DNA

The gene is located in the nucleus of a molecule of DNA, it carries the information of the characteristics of the organism like the blood type or the petal colour. This information is then passed on to the cytoplasm where the genetic information is turned into a protein in which controls the production of the characteristics of the organism.

3.14 the nucleus of the cell contains chromosomes on which genes are located

The chromosomes are the genetic information within the cell

Within the nucleus à chromosomes are found à they are composed of DNA(in a shape known as the double helix) à sections of the DNA are called genes, these carry the information for the construction of à proteins which controls the production of  à the characteristics (e.g. blood type)

Different organisms have different numbers of chromosomes, Humans have 46 whilst cats have 38.

Chromosomes operate in pairs known as the homologous pairs, the homologous nature is based on the length of the chromosome. There are 2 versions each characteristic contained in the gene, which can be found in the same place within the homologous pair.