What Is Reproduction?
All organisms reproduce, including plants and animals. The biological process involves an organism producing and/or giving birth to another organism. Just because all organisms reproduce doesn’t mean the methods of reproduction are the same, however. Plants and animals occupy different phylogenetic kingdoms, but they have evolved reproductive systems that overlap and diverge from each other in several ways. Even within the same kingdom, different species may have different methods of reproduction.
Types of Reproduction
There are two types of reproduction: asexual reproduction and sexual reproduction. The former involves a single parent that produces a genetically identical offspring, whereas the latter involves two parents of the opposite sex, each of whom contributes genetic material to produce a diverse offspring. Different plants and animal can reproduce either asexually or sexually; however, asexual reproduction is more common among plants than animals.
Asexual and sexual reproduction each have benefits and drawbacks. Organisms that reproduce asexually have the advantage of producing several genetically identical offspring quickly and with little energy. On the other hand, the lack of genetic diversity among asexual offspring means they have a lower chance of acclimating to an unstable environment. By contrast, organisms that reproduce sexually have the advantage of producing a genetically diverse offspring, which is able to adapt to its environment. But sexual reproduction comes at a cost, requiring more time and energy to produce an offspring than asexual reproduction.
One difference between plant and animal sexual reproduction concerns fertilization. In flowering plants, the fertilization of an egg is achieved by cross-pollination. This process involves an insect like a bee that transfers the pollen grains from the anther, the male part of a flower, to the stigma, the female part of a flower. Once the pollen lands on the stigma, it passes through a long, tube-like structure called a style to reach the ovaries where fertilization takes place. It should be noted that some plants, called hermaphrodites, have male and female parts on the same plant, and are able to self-pollinate. Animals, by contrast, do not depend on third parties like insects in order to mate. As mobile creatures, animals reproduce by physically interacting with each other and often perform various mating rituals in order to woo potential partners.
Despite differences in the fertilization process, the embryonic development of plants and animals is similar. Once a plant egg is fertilized, it starts developing into a multicellular organism in a way similar to an animal embryo. The only major difference between the two is that a plant embryo is contained within a seed, which provides the nutrients it needs to grow, while an animal embryo develops within an egg, outside the organism, or within a uterus, inside the female parent organism.
Birth and Germination
Plants and animals also differ with respect to how they give birth. Animals exit their mother’s uterus as a newborn or hatch from an egg that has already left the mother’s body. A plant, by contrast, arises by germinating from a seed. The plant releases the seed, which begins to grow once it is in soil and the conditions are right for germination. After the seed has germinated into a plant, it can collect additional nutrients through its roots.
The growth rates of plants and animals also vary. Plants have what is called indeterminate growth, meaning there is nearly no limit to how much they can grow. The extent to which a plant can grow is largely determined by its environment. Consequently, plants do not have a size or age that is deemed normal or mature. The growth rate of mammals, such as humans, is also influenced by environmental factors, like nutrition, but animals cease growing once they have reached adulthood.
As noted earlier, many plants reproduce asexually. There are a variety of ways plants can reproduce without a partner. For example, some nonflowering plants, such as moss and algae, reproduce by spore formation. These plants form several spores, which break off and grow into separate organisms. Other plants, such as strawberries, are able to reproduce asexually through vegetative propagation, either naturally or artificially. This process involves using a vegetative part of a plant, such as a root or stem, to produce a new plant. Alternative artificial methods, such as grafting, involve combining two plants into one by attaching the top part of a plant, called a scion, to the lower part of a plant, called a rootstock.