Pond ecosystem considered as an open ecosystem because pond is always open . There is an interaction of pond with atmosphere , due to which it ecosystem becomes open.
Answer:
Homologous structures have the same ancestry, but may no longer serve the same function. For example, the bones that make up human fingers were inherited from an ancestor that's shared by all mammals.
Formed between two oppositely charged ions
The event last in 15,600 seconds.
Answer: Option B
<u>Explanation:</u>
We know that there is 60 seconds in one minute i.e., 1 minute = 60 seconds
There is 60 minutes in one hour. i.e., 60 minutes = 1 hour.
Given : An event lasts 4 hours and 20 minutes
4 hours contains 240 minutes,

When the above expressed in seconds,
------>eq. 1
When 20 minutes expressed in seconds,
------->eq. 2
Adding both eq. 1 and 2, we get
4 hours and 20 minutes = 14400 + 1200 = 15600 seconds