All organisms go through various changes during their life. We are all growing, right? There are people of different ages around us, like babies, kids, adults, or old people. Animals are growing too. There are baby animals, and adult animals as well. The different periods in life are called stages, or one stage is when being a child, and another stage is being an adult. So all the periods (stages) a living thing goes through during its life is called a life cycle.
In this lesson, we are going to:
A life cycle includes all the stages a living thing goes through from birth to death.
All animals and plants go through a life cycle. We go through a life cycle too. But the life cycle or the stages of different organisms are not the same. For instance, animals and plants, in general, have different life cycles, and the life cycle can be different even between the different groups of animals. Some animals, for example, have a very simple life cycle, like fish, mammals, reptiles, and birds. These animals are born (either alive from their mother or hatched from eggs) and they grow up. Or, they have three main stages, before birth, young and adult, where the young are smaller than the parent but very similar. And some have more complicated life cycles, like amphibians and insects. They undergo huge changes during their life.
Humans go through different stages during their life. Their life cycle begins even before their arrival in the world, or before their birth.
Plants, just as animals and humans, have their unique life cycle. Probably you have seen some seed. Well, the plant's life cycle begins with a seed.
Even if the life cycles differ, they all have something in common: they start with live birth, eggs, or seeds; after they involve multiple steps including reproduction (which is the key to all species' survival); and then they end in death. The cycle repeats for millions of years.
Next, we will discuss the life cycles of animals, humans, and plants, each in more detail.
Animals start from eggs or live birth, then they grow up and mate. Some undergo a simple life cycle, and some undergo a more complicated life cycle. Most animals including fish, mammals, reptiles, and birds have very simple life cycles. But, amphibians and insects have a slightly more complicated life cycle.
Let's understand the life cycles of the animals through examples. So we will try to understand the difference between the simple and more complex life cycles occurring in animals.
We will take two examples, the life cycle of a fish, and the life cycle of a butterfly.
1. The first example is the life cycle of a fish. Did you know that the fish life cycle starts with fish eggs? They are not the same as the eggs you usually see and consume, but you may have seen some. They often look like tiny balls of jelly.
In the above picture, we have an example of the life cycle of a fish. Most fish go through this simple life cycle:
2. The next example is the life cycle of the butterfly. Did you know that butterflies are not so beautiful and colorful at each stage of their life? Or, that they have wings only in one developmental stage? Now look at the butterfly life cycle:
As we can see from the above illustration, for butterflies to grow into an adult they need to go through 4 stages: egg, larva, pupa, and adult. Each stage has a different goal.
Also, we can see that there are huge changes in the form during the stages. When some animals and insects change dramatically during their life cycle, we say they undergo a process called metamorphosis. In some cases, like the above example with the butterfly, when organisms go through four stages during the life cycle, the metamorphosis is complete. Complete metamorphosis can be seen in some other insects too, like mosquitos, bees, beetles. One example from another group of animals, the amphibians, that go under complete metamorphosis, is the frog. But, in some cases, the metamorphosis is incomplete and has only three stages. Grasshoppers are one example of insects that go through an incomplete metamorphosis during their life cycle.
Maybe you will ask: Do humans go under the process of metamorphosis? Well, no. Insects and amphibians are the only organisms that can metamorphose physically.
The human life cycle differs from the animal life cycle. Humans have various stages of growth during their lives, and the change from a child to an adult is slow and continuous. The major stages of the human lifecycle include pregnancy, infancy, toddler years, childhood, puberty, older adolescence, adulthood, middle age, and senior years.
The human life cycle begins with a woman's pregnancy, which occurs in the mother's womb. After approximately 9 months of pregnancy, a baby is born. When a baby is born, until it makes 1 year, it is called an infant. Toddler refers to a child approximately one to 3 years old. The next developmental stage of the human life cycle is childhood. It is roughly divided into early childhood and middle childhood. The teenage years are also called adolescence. People from age 20 to age 60 are considered adults. Adults can be divided into young adults, age: 20-36 years; middle-aged adults, age 36-55 years; older adults, age 55-65 years. And the last stage in humans is old age.
Plants are living organisms, like animals and humans, so they grow and reproduce like any other living organism. Plants start their life from seed (in some nonflowering plants from spores) and undergo several stages until they reach the maturity stage. The stages (with slight differences depending on the type of the plant) are:
When the plant reaches the maturity stage, the process of pollination and seed dispersal occurs, to continue the life cycle of the plant.
Let's summarize:
