Question
How do autotrophs living in an aquatic ecosystem obtain carbon?
A. By diffusion of dissolved carbon dioxide and hydrogen carbonate ions
B. By feeding on heterotrophs and obtaining carbon from carbohydrates
C. By active transport of carbon dioxide directly from the atmosphere
D. By ingesting organisms with carbonate shells
▶️Answer/Explanation
Ans. A
Question
(a) Identify the stage of mitosis labelled X in the image, giving a reason. [1]
(b) Outline the use of a karyogram during pregnancy. [3]
▶️Answer/Explanation
Ans:
a telophase because the chromosomes/chromatids have reached the poles OR «late» anaphase as some chromosomes/chromatids are still moving/tails visible
b
a. is a photograph/diagram of homologous pairs of chromosomes that can be analysed
b. information may be used to determine other chromosome abnormalities/changes in chromosome numbers/possible birth defects
c. Down syndrome/trisomy can be detected if there are three copies of a chromosome OR accept any other valid example Not just “Down syndrome”.
d. other missing or extra pieces of chromosomes can be detected
e. sex can be determined as the Y chromosome is shorter than the X