Video Transcript
Sexual reproduction involves
specialized cells that combine in a process called fertilization. What are these specialized cells
called?
The question is asking us to
determine which specific specialized cells are required for sexual reproduction. In order to work this out, let’s
learn a little bit more about this process.
Sexual reproduction involves two
parents combining half of each of their genetic material to produce offspring. This definition provides us with a
few important facts that we need to take into account, firstly that sexual
reproduction involves two parents. This can be really useful to
organisms as it increases the genetic variation in the offspring produced compared
to asexual reproduction, which only involves one parent. Increased genetic variation makes
individuals more resilient to environmental changes, for example, the introduction
of a new disease into a population. Secondly, sexual reproduction
involves one parent contributing half of their genetic information, which is then
combined to produce offspring.
The combining of genetic
information occurs through a process called fertilization. So we need to work out what these
cells, which contain half the genetic information of each parent, are called. When a cell has half the genetic
material of most of the body cells, only a single set of chromosomes as opposed to
two sets, it is referred to as haploid. This is often represented as n. In humans, there are two different
types of mature haploid cells that can be used in sexual reproduction, depending on
the individual’s biological sex.
Biological females produce haploid
cells called egg cells, which are sometimes called ova, or a singular ovum. These cells are specialized to be
fairly large, and their cytoplasm is filled with nutrients to support the early
development of an embryo. Biological males, on the other
hand, produce haploid cells called sperm cells. These cells are specialized to have
a long tail that allows them to swim toward an egg cell, many mitochondria to
release the energy needed for this journey, and special enzymes that help them to
penetrate an egg cell should they find it. Collectively, the egg cell and the
sperm cell can be referred to as reproductive cells, sex cells, or gametes.
During sexual reproduction, the
sperm cell fertilizes the egg cell and the two haploid cells combine their genetic
information to produce a diploid zygote. This diploid zygote is a cell like
almost all other human body cells that has two sets of chromosomes, which is often
represented as 2n. The zygote can then divide and
specialize to become a fully formed human, full of diploid cells. Therefore, we’ve worked out what
the specialized cells that combine in fertilization are called. They are called gametes.
