paper 2 Flashcards
(46 cards)
What is DNA?
A molecule that carries genetic information in the form of genes.
What is a gene?
A section of DNA that codes for a specific protein.
What is a chromosome?
A long molecule of DNA containing many genes.
What is a dominant allele?
An allele that is always expressed, even if only one copy is present.
What is a recessive allele?
An allele that is only expressed if two copies are present.
What is natural selection?
The process where organisms better adapted to their environment survive and reproduce.
What is selective breeding?
Humans breeding organisms for desirable traits.
What is genetic engineering?
Modifying an organism’s genome to introduce desirable traits.
What is homeostasis?
Maintaining a stable internal environment.
What are three factors controlled by homeostasis?
Blood glucose levels, body temperature, water levels.
What is the function of the nervous system?
To detect stimuli and coordinate responses.
What hormone controls blood sugar levels?
Insulin lowers blood sugar; glucagon raises blood sugar.
What are the four main hormones in the menstrual cycle?
FSH, LH, oestrogen, progesterone.
What is a food chain?
A diagram showing energy transfer between organisms.
Why is biodiversity important?
It ensures ecosystem stability and resilience to changes.
How does deforestation affect the environment?
Reduces biodiversity, increases CO₂ levels, disrupts ecosystems.
What is the role of decomposers?
Break down dead organisms, returning nutrients to the ecosystem.
What is the greenhouse effect?
The trapping of heat in the Earth’s atmosphere due to greenhouse gases.
What is a producer in a food chain?
An organism that makes its own food (e.g., plants via photosynthesi
What are the four bases in DNA?
Adenine, Thymine, Cytosine, Guanine (A-T, C-G).
How are fossils formed?
when the remains of a plant or animal are buried in sediment and then transformed into rock.
Why is the fossil record incomplete?
Many organisms decayed or were destroyed; soft tissues rarely fossilize.
What is extinction?
When no individuals of a species remain
How do fossils provide evidence for evolution?
They show gradual changes in species over time
