Edexcel A level Biology Exam Study Guide Solutions

Edexcel A level Biology Exam Study Guide Solutions Molecular phylogeny - ANSWER-It compares the structure of a particular molecule from different organisms to discover their degree of evolutionary relation. Somatic cell - ANSWER-A cell in an organism which isn't a gamete. DNA - ANSWER-Deoxyribose nucleic acid. Carries the genetic information for cells and some viruses. mRNA - ANSWER-Messenger ribose nucleic acid (single stranded). The product of transcription. Speciation - ANSWER-The process through which a species is created Sympatric - ANSWER-Due to reproductive isolation. Allopatric - ANSWER-Due to geographical isolation Niche - ANSWER-The role an an organism in an ecosystem. Habitat - ANSWER-The natural environment in which a species lives. Biodiversity - ANSWER-The diversity of plant and animal life in a particular habitat Ecosystem - ANSWER-Organisms and their interactions with biotic and abiotic factors. Carpentered world hypothesis - ANSWER-People who live in a world with many straight lines and right angles tend to interpret obtuse and acute angles as right angles. Copyright © OLIVIAWEST2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED Copyright ©Stuvia International BV Page 2/7 Muller-Lyer Illusion - ANSWER-An illusion where a man could be pointing at two different objects, but depth cues let us know it is the object in the foreground he is pointing to. Inhibitory synapse - ANSWER-These are synapses that make it less likely that an action potential will happen in the post synaptic membrane. Auxins - ANSWER-Plant hormones that stimulate growth by causing cells to elongate. Indoleacetic acid (IAA) - ANSWER-A specific type of auxin. Summation - ANSWER-When the effect of multiple impulses adds up. Spatial summation - ANSWER-Summation from many impulses from different neurons. Temporal summation - ANSWER-Summation from multiple consecutive impulses from a single neuron. Excitatory synapse - ANSWER-These synapses make the postsynaptic membranes more permeable to sodium ions. Synapse - ANSWER-Where two neurones meet. Synaptic cleft - ANSWER-The gap in a synapse. Nodes of Ranvier - ANSWER-These are gaps in the myelin sheath where depolarisation can occur. Saltatory conduction - ANSWER-This is the conduction of an impulse by 'jumping' between the nodes of ranvier. Depolarisation - ANSWER-When the polarisation across the cell membrane is reversed, making the inside of the axon positive and the outside negative. Copyright © OLIVIAWEST2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED Copyright ©Stuvia International BV Page 3/7 Hyperpolarisation - ANSWER-When the potential difference in the cell is more negative than the resting potential due to excess potassium ions moving out since the membrane is now highly permeable. Voltage-dependent gated channels - ANSWER-These are channels which open due to changes in the voltage across the membrane. Positive feedback - ANSWER-When one change leads to further change with the same effect. Repolarisation - ANSWER-When the cell returns to having a resting potential of -70mV after spiking to about +40mV. Action potential - ANSWER-The change in voltage from +40 to -70mV that occurs during repolarisation. Resting potential - ANSWER-The potential difference inside the axon when it is at rest. Approx - 70mV. Photoreceptors - ANSWER-Light receptors. Antagonistic muscles - ANSWER-Muscle pairs arranged to work against each other to move a joint. Reflex arc - ANSWER-A simple nerve pathway responsible for reflexes. Reflex - ANSWER-An involuntary, rapid response to a stimuli. Sensory neuron - ANSWER-A neuron which carries impulses from sensory cells to the CNS. Relay neuron - ANSWER-These neurons are mostly found within the CNS and they connect neurones together. Copyright © OLIVIAWEST2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED Copyright ©Stuvia International BV Page 4/7 Myelin sheath - ANSWER-The fatty insulating layer made up of schwann cells that wraps around the axon to protect and speed up the impulse. Motor neurone - ANSWER-A neuron with the cell body situated in the CNS, with axons that extend out to the effectors (muscles and glands) Dendrites - ANSWER-These conduct impulses towards the cell body. Axon - ANSWER-This conducts an impulse away from the cell bo