When the temperature reaches 0˚C (32˚F), the top layer of the lake freezes and turns into ice. In solid form, water molecules are less dense and thus ice floats on the top of the lake.
This solid barrier prevents any wind-induced mixing as well as protects the relatively warm water underneath. Furthermore, light is also blocked so that photosynthesis is inhibited during this period. As the lake water is separated from the atmosphere, no direct oxygen diffusion occurs.
All these factors together causes a more even distribution of nutrients and gases in a lake in winter.
Answer:
<u>a) strong joints with restricted movement.</u>
Explanation:
Joints which are closely fitted cannot allow free movement because movement requires space in the joint so the bones can move in this space. So a closely fitted joint allow restricted or no movement at all. Weak joints with restricted movements are called weak because they are not well fitted closely. Strong joints with restricted movement is closely fitted, one of the example is joints of skull.
Geographical Isolation is the mechanism that might have led to the appearance of the Hawaiian honeycreeper.
Geographical Isolation is the term used that refers to a population of animals, plants, or other organisms that are separated and unable to exchange genetic materials with other organism of the same species.
Geographical Isolation may be a result of coincidence or accident.
Here are some factors of Geographical Isolation:
1) Isolation by barriers
2) Isolation by distance
3) Isolation after an Event
4) Isolation by separation
Answer:
d. Character displacement
Explanation:
Character displacement is the phenomenon in which the similar species living in the same geographical region with similar niches differentiate in order to reduce their niche overlap and avoid competitive exculsion. Just like in this case of two- spot and three -spot avenger beetles as their timmings for hunting is different where their ranges overlap. So it's the good example of character displacement,
Answer: exocrine glands
Explanation: Exocrine gland secrete substances to an epithelial surface through a channel.
The sebaceous and sweat glands associated with the skin also secrete substance to skin surfaces via ducts/ channels and are classified as endocrine gland. There are two glands in the human body Exocrine gland and Endocrine gland.
Endocrine gland secrete substance into the bloodstream directly. Examples of exocrine glands are sweat, salivary, mammary, sebaceous, and mucous.
liver and pancreas are both exocrine and endocrine glands simultaneously.
As exocrine gland, the liver secrete bile and the pancrease secrete pancreatic juice into the gastrointestinal tract through channels. While as endocrine gland they secrete other substances directly into the bloodstream.
