Unit 2.4: Variation & Inheritance Flashcards
Describe how sexual reproduction contibutes to variation within a species.
Sexual reproduction creates variation in a species by combining genetic information
Define polygenic inheritance.
Features which are controlled by many genes
What type of variation is shown in characteristics controlled by polygenic inheritance?
Continuous variation
What is a gene?
A section of DNA
What is an allele?
Different forms of the same gene
What is a phenotype?
The colour an organism shows
Describe a dominant allele
The allele that shows up in the phenotype maskinb the ressecive
Describe a recessive allele?
The allele that doesn’t show in the phenotype as it is masked but still present in the genotype
What is the term used to describe two alleles which are the same?
Homozygous
What is the term used to describe two alleles which are different?
Heterozygous
What is the function of the upper epidermis?
The protected layer that lets light through
What is the function of the palisade mesophyll?
Photosynthesis
What is the function of the spongy mesophyll?
Photosynthesis
What is the function of the vein?
To allow water to be transported to be a leaf
What is the function of the guard cells?
To control the opening and closing of stomata
What is the function of the stomata?
Tiny holes which water and oxygen leave and carbon dioxide enetrs the leaf
What vessels are found in veins?
xylem and phloem vessel
What part of the plant is involved in water transport?
roots, stem and leaves
Describe how the root is specialised for its role of water absorption.
Roots have root hairs which increase the surface area
Name the vessel responsible for water transport.
xylem
Describe the structure of xylem vessels.
Dead hollow tube
contains ligin
Why are xylem cells lignified?
To withstand pressure change as water moves through the plant
State the name of the vessels responsible for sugar transport.
phloem
Describe the structure of phloem vessels.
Alive sieve plates (not done)
What is transportation?
The process of water moving through a plant and is evaportated through the stomata
Explain how root cells transport water.
It takes water from the soil by osmosis
Explain how xylem transport water.
The cohesive forces link the water molecules together and pull them up the xylem vessels
Explain how stomata transport water.
water evaporates
Name the external factors that affect the rate of transpiration.
Temperature
Humidity
Wind speed
Describe the best conditions for maximising the rate of transpiration.
Large surface area
High temperature
High wind speed
Low humidity
Name the apparatus used to measure transpiration.
Potometer
How is the rate of transpiration calculated?
Water loss/time
