Answer:
The answers are matched as follows:
African forests have been hunted to near extinction levels to obtain ivory-------------->human exploitation
The eruption of mount Saint Helens destroyed some populations of conifers------> natural disasters
An infection with a fungus reduced the population of North American Elm trees ----> disease
Increasing global temperatures have altered migration patterns of humpback whales ------>climate change
Answer:
These structures that protect the sponges from most predators, but not turtles, are spicules.
Explanation:
Sponges <em>skeleton</em> is composed of <em>calcium carbonate and siliceous</em> micro-structures called <u>spicules</u>. Their morphology is so varied that it is used in taxonomy for identification and classification.
There are different kinds of spicules:
- <em>Monoaxonic spicule</em>: needle-shaped, straights or curves
- <em>Tetraxonic spicules:</em> they have four prolongations
- <em>Triaxonic or Hexaxonic spicules</em>
- <em>Poliaxonic spicules </em>
Two terms can be applied to any of these spicules kinds:
- <em>Megaspicules</em>: They are elongated and compose the main architecture of the sponge skeleton
- <em>Microspicules</em>: Variable in shape and size, with ancillary functions
Sponges have few predators thank to the spicule structures and their high toxicity. Many of them are capable of perforating soft tissues and producing urticant substances.
Answer:
Autonomic regulation of heart is via two reflex centers that are found in medulla oblongata
Explanation:
Medulla oblongata contain long stem that makes the upper part of brain case and this is a cone shaped structure which is responsible for autonomic regulation like controlling heart rate,vomiting,respiration,breathing etc.
The heart rate is controlled by autonomic nervous system that are mainly sympathetic and parasympathetic nervous system that releases hormones like catecholamine (epinephrine and non epinephrine) which helps in controlling the heart rate.
Medulla oblongata mainly connects the brain with the spinal cord that are responsible for responsible for the autonomic functions which contain -
Controlling the ventilation via signalling system regulated by chemo receptors which detects change in acidity of the blood.
Acts on cardiovascular centers.
Controlling the reflex centers like vomiting,coughing,sneezing,swallowing etc.
Answer:
Nowadays, we are having organic vegetables.