Video Transcript
Extinctions can also be caused by
human interference. Which of the following is a human
activity that could result in mass species extinction? (A) Gardening, leading to the
removal of some plant species. (B) Reforestation to reestablish
lost habitats for species. (C) Storing seeds in gene banks,
which requires the removal of seeds from existing plants. Or (D) pollution, leading to
warming the global temperature.
This question asks us to select the
human activity that could result in a mass species extinction. But what is a mass species
extinction?
Extinction is defined as the
termination of existence of all the members of a kind of organism, usually a
species, due to all the living members of that species dying out. A mass extinction is when a large
proportion of species go extinct in a relatively short amount of time. Let’s have a look at each of the
answer choices in turn and decide which one could result in a mass species
extinction.
Gardening, leading to the removal
of some plant species, could result in the removal of one or more species from a
very small area in a garden. But even this is unlikely to remove
all of one type of species from one garden. So this could not result in the
extinction of even only one species. This could not result in a mass
species extinction, and we can therefore eliminate answer choice (A).
Answer choice (B) refers to
reforestation. This is the planting of trees to
increase the number in a forest where the number of trees has previously
decreased. Reforestation provides more
habitats for a wide range of forest-dwelling species. Reforestation therefore reduces the
risk of extinction. We can now eliminate answer choice
(B).
Answer choice (C), storing seeds in
gene banks, is a method with the aim of preventing the extinction of species. Seeds can be stored in gene banks
for long periods of time. In the future, these seeds could be
used to increase the population of a species should it become endangered or at risk
of going extinct. Even though seeds are removed from
existing plants, plants often produce many seeds. So the removal of seeds alone will
not result in extinction. We can therefore eliminate answer
choice (C).
Our final answer choice, pollution,
leading to warming the global temperature, could impact a vast number of
species. Rising temperatures can lead to ice
melting in polar regions. This reduces habitats for polar
organisms, such as polar bears and penguins. Melting polar ice also leads to an
increase in sea levels, which could lead to the flooding and therefore destruction
of many coastal habitats, affecting a wide range of species. Increasing global temperature means
an increase in the temperature of the oceans, too. This could impact many sea-dwelling
organisms. A change in temperature impacts the
ocean currents. This can affect the distribution of
organisms and disrupt food chains.
Higher temperatures also lead to an
increase in the frequency and severity of extreme weather events. More floods, storms, and heat waves
can all have a huge impact on many species. Huge areas that are home to a
diverse range of organisms can be destroyed in a short period of time.
We have discussed only a few
examples of the impact an increase in the global temperature could have. The effects do have the potential
to result in the extinction of a high proportion of species. Many different habitats could be
damaged or destroyed, and many different food chains could be disrupted, impacting
many different species. So the human activity that could
result in a mass species extinction is given in answer choice (D), pollution,
leading to warming the global temperature.
