S4 - Biology Test (4) Flashcards
What is a gene?
The unit of inheritance & a section of DNA that codes for a specific protein
What are alleles?
Different forms of the same gene
What does it mean if a gene is dominant?
Hides the presence of a recessive gene
What does it mean if a gene is recessive?
Hidden by dominant genes
What is the genotype of an organism?
The genes an organism has
What is the phenotype of an organism?
The physical appearance of genes
What is the difference between homo and hetero zygous genes?
homo = contains 2 of the same type of allele of a gene
hetero = contains both a dominant and recessive allele of a gene
What is a cause of variation within a species?
Combining genes from 2 parents
Why does variation within a species occur?
Because fertilisation is a random process
What is variation?
The differences that exist between and within populations
What are the 2 types of variation?
- Continuous
- Discrete
What is continuous variation?
A polygenic inheritance of characteristics showing continuous variation where there is a range of values between a max. and a min.
What is discrete variation?
A single gene inheritance of characteristics showing discrete variation where measurements fall into distinct groups
What are a plants organs?
- Roots
- Stems
- Leaves
What is the function of the upper epidermis?
Has a waxy layer that reduces water loss
What is the function of the palisade mesophyll layer?
Absorbs light for photosynthesis
What is the function of the spongy mesophyll layer?
The air spaces allow gases to reach leaf cells for photosynthesis
What is the function of the lower epidermis?
It contains pores called stomata which allow gases to diffuse in and out of the leaf
What is the function of the stomata?
It allows water vapour to be released and is the site of gas exchange
What is the function of guard cells?
Control the opening and closing of the stomata
Why do plants need transport systems?
To make sure the essential materials can reach all cells and so that waste materials can be removed safely
What are the essential materials plants need?
Sugar and water
Name what each arrow is pointing to
Name what each arrow is pointing to
Why do plants need water and where is it needed?
- for photosynthesis & to help transport minerals (N, K, P) throughout the plant
- the roots, stems and leaves
Where does water enter a plant from?
The root hair cell
What is the function of the root hair cell?
To absorb water from surrounding soil via osmosis
How does the shape of a root hair cell help absorption?
It has a large surface area