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Name the 3 types of neurones in a reflex arc and describe their roles.
The sensory neurone carries impulses from receptors to the CNS, the relay neurone transfers the signal within the spinal cord, and the motor neurone sends impulses to the effector such as a muscle or gland.
How is a signal passed between neurones at a synapse?
Neurotransmitters are released from one neurone, cross the synapse, and bind to receptors on the next neurone, causing an electrical impulse to continue.
What is a food web and how can removing one species affect it?
A food web shows how different food chains are linked. Removing one species can affect the balance of predators and prey because they all depend on each other.
How do photosynthesis and respiration cycle carbon?
Photosynthesis removes carbon dioxide from the atmosphere, while respiration by plants and animals releases it back into the air.
How does natural selection cause evolution?
Natural selection happens when variation exists in a population. The best-adapted individuals survive and reproduce, passing on their genes. Over time, the species evolves.
How do insulin and glucagon control blood glucose?
Insulin lowers blood glucose by converting glucose into glycogen for storage. Glucagon raises it by turning glycogen back into glucose. Both hormones are made by the pancreas.
What helps a camel survive in the desert?
A camel’s sandy colour helps it blend in, its humps store fat that can be used for energy and water, and features like long eyelashes and wide feet help it live in sandy, hot conditions.
Why don’t antibiotics work on viruses?
Antibiotics don’t work on viruses because viruses live inside body cells and don’t have structures like cell walls that antibiotics usually target.
How does antibiotic resistance develop?
Some bacteria mutate and become resistant. When antibiotics are used, they kill non-resistant bacteria but leave the resistant ones to survive and multiply.
What conditions speed up decay?
Decay happens faster in warm, moist conditions with plenty of oxygen.
What’s the function of each part in a reflex arc?
The receptor detects the stimulus, the sensory neurone carries the message to the CNS, the relay neurone processes the signal, the motor neurone sends the message to the effector, and the effector produces a response.
How does genetic variation arise?
Genetic variation happens when gametes from two parents combine during sexual reproduction, mixing their genes.
What’s the difference between dominant and recessive alleles?
A dominant allele only needs one copy to be shown, while a recessive allele needs two copies to appear in the phenotype.
Give 2 organisms that reproduce asexually and a benefit of it.
Strawberry plants and malaria parasites reproduce asexually. The advantage is that it’s quick and produces genetically identical offspring.
One advantage and one disadvantage of sexual reproduction?
The advantage of sexual reproduction is genetic variation. The disadvantage is that it’s slower and requires two parents.
Why is not all energy passed along a food chain?
Not all energy is passed on because some parts like bones or fur aren’t eaten, and some energy is lost through heat and respiration.
How can temperature or water changes affect where organisms live?
Organisms may adapt, move to new areas, or die if the environmental changes make their habitat unsuitable.
Give 2 human activities that reduce biodiversity.
Deforestation and burning fossil fuels both reduce biodiversity by damaging habitats and contributing to climate change.
