Species richness in a community drastically declines after the removal of one species. This species ...

Species richness in a community drastically declines after the removal of one species. This species was likely a(n) ____.
 
  a. mutualistic species
  b. indicator species
  c. pioneer species
  d. keystone species
  e. exotic species

Question 2

Synaptic integration means that:
 
  a. all positive or excitatory stimuli are added together
  b. the positive and negative ions neutralize each other
  c. excitatory and inhibitory signals are combined in a postsynaptic neuron
  d. adjacent neurons interact so that excitatory and inhibitory stimuli cancel each other
  e. one neurotransmitter signal is received at a time