Gosse biology homeostasis mark scheme-
guaranteed success
Potato blight is a disease of potato plants.
Potato blight is caused by the fungus Phytophthora infesting.
What is the genus of the fungus that causes potato blight? (1) - Correct Answer
Phytophthora (1)
The fungus grows near the surface of the potato. How does growing near the surface
help the fungus to respire? (1) - Correct Answer the fungus can get oxygen from the
air (1)
A farmer sprays his potato plants with a pesticide. The pesticide kills the fungus that
causes potato blight. Spraying the crop with a pesticide could decrease biodiversity in a
river flowing through his farm. What does 'biodiversity in a river' mean? (1) - Correct
Answer the variety of species of organisms in the river (1)
The farmer sprayed pesticide on his potato plants. The next day it rained heavily.
Explain why the biodiversity in the river decreased. (2) - Correct Answer pesticide
washed into river (1)
pesticide kills (some) organisms / plants / animals in river (1)
Potatoes can also reproduce asexually. Potatoes from one plant can be planted in the
ground to produce new potato plants. All the new plants from a parent plant that is
resistant to blight will also be resistant to blight. Explain why. (2) - Correct Answer no
fusion of gametes (1)
or
(asexual reproduction involves) mitosis (1)
(so) offspring are genetically identical (to parent plant) (1)
Name the structures inside the cell nucleus that contain DNA. (1) - Correct Answer
chromosome (1)
A gene is a length of DNA. What type of substance does a gene code for? (1) - Correct
Answer protein (polypeptide) (1)
Most human body cells contain 6 × 10-12 grams of DNA. What mass of DNA will a
human sperm cell contain? (1) - Correct Answer 3 × 10 −12 grams (1)
, What is the name of the type of cell division that produces sperm cells? (1) - Correct
Answer meiosis (1)
Without medical treatment, people with sickle cell anemia are frequently ill and have a
reduced life expectancy.
The malarial parasite cannot live in the red blood cells of a person who has the HS
allele.
A scientist stated: 'It is an advantage for people to have the HS allele in countries where
malaria occurs.'
Evaluate the scientist's statement. (3) - Correct Answer HAHS do not get malaria (1)
HAHS survive sickle cell anemia (1)
HAHA may die from malaria (1)
HSHS may become (severely) ill with sickle cell anemia (1)
if parents HAHS then some offspring survive both malaria and sickle cell anemia (1)
During meiosis a cell divides twice. How many sperm cells are formed when a cell
divides by meiosis? (1) - Correct Answer four (1)
Human body cells contain 46 chromosomes. How many chromosomes are in each
human egg cell? (1) - Correct Answer 23 (1)
A genetic disorder develops as a result of a change in a gene. What scientific term
describes a change in a gene? (1) - Correct Answer mutation / mutated (1)
People with a family history of some genetic disorders are offered embryo screening.
Suggest one way embryo screening can help people with a family history of a genetic
disorder. (1) - Correct Answer a different form of a gene (1)
Describe the shape of a DNA molecule. (2) - Correct Answer any two from
double (1)
helix (1)
long / thin (1)
DNA codes for a sequence of amino acids. Which part of DNA forms the code for a
particular amino acid? (1) - Correct Answer bases (1)
Which substance is produced when amino acids are joined together? (1) - Correct
Answer protein (1)
Why is DNA described as a polymer? (1) - Correct Answer many (joined) nucleotides
or monomers (1)
Describe the structure of a nucleotide. (1) - Correct Answer phosphate (1)
(phosphate attached to a) sugar (1)
(which has 1 of 4) base(s) (attached to sugar) (1)
(bases) are A, C, G and T (1)
guaranteed success
Potato blight is a disease of potato plants.
Potato blight is caused by the fungus Phytophthora infesting.
What is the genus of the fungus that causes potato blight? (1) - Correct Answer
Phytophthora (1)
The fungus grows near the surface of the potato. How does growing near the surface
help the fungus to respire? (1) - Correct Answer the fungus can get oxygen from the
air (1)
A farmer sprays his potato plants with a pesticide. The pesticide kills the fungus that
causes potato blight. Spraying the crop with a pesticide could decrease biodiversity in a
river flowing through his farm. What does 'biodiversity in a river' mean? (1) - Correct
Answer the variety of species of organisms in the river (1)
The farmer sprayed pesticide on his potato plants. The next day it rained heavily.
Explain why the biodiversity in the river decreased. (2) - Correct Answer pesticide
washed into river (1)
pesticide kills (some) organisms / plants / animals in river (1)
Potatoes can also reproduce asexually. Potatoes from one plant can be planted in the
ground to produce new potato plants. All the new plants from a parent plant that is
resistant to blight will also be resistant to blight. Explain why. (2) - Correct Answer no
fusion of gametes (1)
or
(asexual reproduction involves) mitosis (1)
(so) offspring are genetically identical (to parent plant) (1)
Name the structures inside the cell nucleus that contain DNA. (1) - Correct Answer
chromosome (1)
A gene is a length of DNA. What type of substance does a gene code for? (1) - Correct
Answer protein (polypeptide) (1)
Most human body cells contain 6 × 10-12 grams of DNA. What mass of DNA will a
human sperm cell contain? (1) - Correct Answer 3 × 10 −12 grams (1)
, What is the name of the type of cell division that produces sperm cells? (1) - Correct
Answer meiosis (1)
Without medical treatment, people with sickle cell anemia are frequently ill and have a
reduced life expectancy.
The malarial parasite cannot live in the red blood cells of a person who has the HS
allele.
A scientist stated: 'It is an advantage for people to have the HS allele in countries where
malaria occurs.'
Evaluate the scientist's statement. (3) - Correct Answer HAHS do not get malaria (1)
HAHS survive sickle cell anemia (1)
HAHA may die from malaria (1)
HSHS may become (severely) ill with sickle cell anemia (1)
if parents HAHS then some offspring survive both malaria and sickle cell anemia (1)
During meiosis a cell divides twice. How many sperm cells are formed when a cell
divides by meiosis? (1) - Correct Answer four (1)
Human body cells contain 46 chromosomes. How many chromosomes are in each
human egg cell? (1) - Correct Answer 23 (1)
A genetic disorder develops as a result of a change in a gene. What scientific term
describes a change in a gene? (1) - Correct Answer mutation / mutated (1)
People with a family history of some genetic disorders are offered embryo screening.
Suggest one way embryo screening can help people with a family history of a genetic
disorder. (1) - Correct Answer a different form of a gene (1)
Describe the shape of a DNA molecule. (2) - Correct Answer any two from
double (1)
helix (1)
long / thin (1)
DNA codes for a sequence of amino acids. Which part of DNA forms the code for a
particular amino acid? (1) - Correct Answer bases (1)
Which substance is produced when amino acids are joined together? (1) - Correct
Answer protein (1)
Why is DNA described as a polymer? (1) - Correct Answer many (joined) nucleotides
or monomers (1)
Describe the structure of a nucleotide. (1) - Correct Answer phosphate (1)
(phosphate attached to a) sugar (1)
(which has 1 of 4) base(s) (attached to sugar) (1)
(bases) are A, C, G and T (1)
