Top answers

How do populations of bacteria develop antibiotic resistance?

There is VARIATION amongst the population due to naturally occuring MUTATION during DNA replication . The antibiotics act as a SELECTION PRESSURE, so only the bacteria with the allele for antibiotic resistan...
LG
Answered by Leila G. • Biology tutor
3330 Views

What endocrine glands regulate sexual activity in males? How does this regulation work and what hormones are involved?

Here are the endocrine glands that regulate sexual activity in males: 1) the hypophysis (aka. the pituitary); 2) the adrenal glands; 3) the gonads (testicles). - - - - - - - - - - - - - It's pretty much all ...
LT
Answered by Lydia T. • Biology tutor
7620 Views

During the cardiac cycle , there is a delay between the excitation of the atria and excitation of the ventricles. Explain how this is achieved and why this delay is essential.

Excitation from SAN (sino-atrial node) spreads across atria , causing them to contract first. The excitation is conducted to the AV (atrio-ventricular) node, which introduces a 0.12s delay . This refractory ...
JE
Answered by Jane E. • Biology tutor
15874 Views

How does a signal move from one neurone to another and how does this process change for different motor responses?

The transmission of an action potential- the signal- from one neurone to another occurs over the synapse. The structure of a synapse is as follows; there is a presynaptic bulb, a post synaptic bulb and the s...
AH
Answered by Amy H. • Biology tutor
3435 Views

Explain the process of muscle contraction in a myofibril following nervous stimulation.

Muscle contraction can be explained using the 'Sliding Filament Hypothesis'. Following nervous stimulation, a nerve impulse will be transmitted to a neuromuscular junction. This will cause a release of the n...
LM
Answered by Lydia M. • Biology tutor
7955 Views