<u>Answer:</u>
Cyanobacteria start producing pure oxygen around 200 million years ago.
<u>Explanation:</u>
Many scientists believed that Earth did not have any oxygen. Cyanobacteria or the blue green algae are the microbes which produced oxygen for the first time with the help of photosynthesis. This was around 4.5 billion years ago: after Hadean eon.
They were very simple, but they produced oxygen in the early earth’s atmosphere. So, they brought evolution on earth. This “blue-green algae” exists in salt water, rocks and soils and play a major role in maintaining the ecosystem.
There are no statements given however a centriole is made up of microtubules triplets in a 9+0 pattern (I am unsure of what level of depth is required)
Answer:
Stimuli must be sensed in order to respond.
Explanation:
Classical conditioning can be defined as a learning process which typically involves repeatedly pairing two stimuli: conditioned stimulus and unconditioned stimulus.
Simply stated, it is a learning procedure that helps us to understand when a neutral stimulus is paired with a conditioned response.
An example is the process of salivating in response to the aroma of a meal being prepared in the kitchen.
Also, operant conditioning can be defined as an associative learning process which involves reinforcing the strength of a behavior.
Stimulus in biology can be defined as an obvious change in either the chemical or physical structure of an organism' environment (either external or internal). Thus, all living organisms (both animals and plants) respond to changes in their environment and consequently, an appropriate response or reaction is made. Also, stimulus arising from within the organism is known as internal stimulus while those from its environment are known as the external stimulus.
In organisms, the specialized cells that detect stimulus are generally known as sensory receptors while a group of these receptors is referred to as sense organ.
Hence, the senses are necessary for behavior because stimuli must be sensed in order to respond.
