How do we compute the age of a living tree?
To estimate the age of a living tree, following steps are required
(i) Measure the circumference of the tree trunk (at about 4.5 feet above the ground).
(ii) Calculate the diameter of the trunk. This is done by dividing the circumference by 3.14. Divide this (i.e., diameter) by 2 to get the radius.
(iii) Determine the growth factor. A tree's growth factor is the measurement of the width it gains annually. The trees's growth factor can be seen from the data available or by measuring the rings of a dead tree from the same species.
(iv) Multiply the diameter and the tree species average growth factor and the so done calculating suggest the approximate age of the tree in years.
Give an example for convergent evolution and identify the features towards which they are converging.
When unrelated animals converging to the same form or structure, that is very adaptive in their common environment. It is called convergent evolution, e.g., Australian marsupials and placental mammals.
Such as (placental wolf and Tasmanian wolf). These two sub-classes of mammals have adapted in similar ways to a particular food supply, locomotor skill or climate.
Their resemblances in overall shape, locomotor mode and feeding and foraging are superimposed upon different modes of reproduction, the feature that accurately reflects their distinct evolutionary relationships.
How do we compute the age of a fossil?
The age of a fossil can be computed by radioactive dating (also called radiometric dating). It is a technique based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates. Among the best known techniques are radiocarbon dating, potassium-argon dating and uranium lead dating.
What is the most important pre-condition for adaptive radiation?
Conditions promoting adaptive radiation are much of the diversity of life originated through episodes of adaptive radiation during periods when ecological space became available for diversification. There are two primary mechanisms through which ecological space can become available.
(i) intrinsic changes in organisms.
(ii) extrinsic effects, including environmental change and colonisation of isolated landmasses.
How do we compute the age of a rock?
The age of a rock in years is called its absolute age. It is determined by the natural radioactive decay of certain elements, e.g., uranium, when decays turns into lead. The parent atoms of uranium are converted into daughter atoms of lead over a fixed interval of time. This interval is the decay constant.
The ratio of parent-daughter atoms changes in a quantity that can be measured.
The radioactive half-life (the amount of time required for one half of the parent atoms to beonverted to daughter atoms) is used to calculate the age of the rock.