Video Transcript
Which of the following best
describes a biological tissue? (A) A tissue is a group of cells
that work together to perform a certain function. (B) A tissue is a group of organs
that work together to perform a particular function. (C) A tissue is a section of an
organ that has multiple, varied functions. Or (D) a tissue is a collection of
random cells that perform different, independent functions.
This question is asking us about
the definition for the term tissue, which is one of the levels in the biological
organization of living things. To answer this correctly, let’s
review some key points about this organization and in particular the role of tissues
in it.
Cells are the smallest biological
unit of an organism. Groups of cells then work together,
forming tissues. There are two main types of tissues
in plants: simple tissues and compound, or complex, tissues. Simple tissues are composed of
cells that are both functionally and structurally similar. They are located in every part of
the plant and have many different roles. The three simple tissues in plants
are parenchyma, collenchyma, and sclerenchyma.
Parenchyma tissue is often found in
leaves and stems and has varied functions that include photosynthesis as well as
water and nutrient storage. Collenchyma tissue is made up of
cells with a thick cell wall and functions in giving a plant support, as well as
elasticity, to growing regions. Sclerenchyma tissue consists mainly
of cells with heavily thickened, lignified cell walls. This tissue’s role is to give the
plant mechanical strength and structural support.
Compound tissues are complex in
nature and made up of different cells with varied structures and functions. However, they still work together
to carry out a role within the plant. Examples of such tissue are xylem
and phloem that make up the vascular bundle or transport tissues in plants. The xylem tissue’s function is to
transport water and dissolved minerals from the roots to the other parts of the
plant. The phloem tissue’s function is to
transport sugars and amino acids from the site of photosynthesis, usually in the
leaves, to the parts of the plant that require them.
A group of specialized tissues that
work together to perform specific functions is an organ. For example, the leaf of a plant is
made of epidermal tissue, mesophyll tissues, vascular bundles, as well as the three
simple plant tissues. They work together to enable the
plant to efficiently photosynthesize to produce food for the plant. Groups of organs working together
then form organ systems. Plants have both a root and shoot
organ system.
Now that we have reviewed these key
facts, let’s look at the question again. The question asks which statement
describes biological tissues the best. We now know that option (B), a
group of organs working together, actually refers to an organ system. So we can rule this option out. We also now know that an organ is
made up of specialized tissues, working together to carry out a function. So we can also rule out (C).
This leaves us with options (A) and
(D). But as we saw with the xylem and
phloem, even though they were made up of more than one type of cell, they were still
working together to carry out a specific function. So this rules out option (D). We can therefore conclude that
option (A) is the correct answer. A tissue is a group of cells that
work together to perform a certain function.
