The life cycle of an animal includes the different stages in its life span. Life cycles vary depending on the species of animals. It can be as short as just about a few weeks for insects. Despite the very time differences, all animal cycles begin with a growth and development process, which is then followed by reproduction. The reproductive stage in the cycle of life marks the end of the cycle, and many animals often die after they have reproduced only once.
Beginning of Life
Most animal species begin their life as a single egg cell, which is then fertilized by a sperm cell. The growth process differs in speed depending on the species. Some animals are born in less than a week of conception, whereas others are born nearly two years afterward. Animals are born in very different ways depending on their group. Mammals give birth to live young, whereas birds, fish, and reptiles lay eggs from which their young hatch out. In some egg-laying animals such as sharks, the eggs are laid and incubated inside the body of the mother shark who then gives birth to live young.
Life Span
Generally, the amount of time an animal will live for is greatly dependent on the shape and size of its body. Blood temperature also plays an important part in an animal’s life span as slow-moving, cold-blooded animals such as reptiles tend to live longer than the more frantic warm-blooded flyers such as birds. Some animals also live longer than those animals who are weak and vulnerable in their environment.
Four Stages of the Life Cycle
Life cycles mostly happen in four stages Some animals, such as mealworm beetles, butterflies, and mosquitoes, have four stages in their life cycles. These four stages are the egg, the larvae, the pupa, and the adult. The young stages of these animals look different from the adult ones.
Life Cycle
The life cycle in biology refers to the series of changes that the members of a species undergo as they go from the beginning of a given developmental stage into the inception of the same developmental stage in the subsequent generation.
In many simple organisms including bacteria and several protists, the life cycle completes within one single generation. The process in the organism begins with the fission of an existing individual and the new organism grows to maturity and then splits into two newer individuals and completes the life cycle. In the higher animals, the life cycle encompasses a single generation as well. The specific animal begins with the fusion of male and female sex cells that are called gametes. This grows to reproductive maturity and then produces gametes, at the point when the cycle begins afresh by assuming that the fertilization takes place. In this article, we will learn about the animal life cycle, the list of life cycles, and the importance of the animal life cycle.
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Why are Life Cycles Important to Living Things
A life cycle determines the series of stages that an individual organism passes through from the time it is conceived to the time it produces offspring of its own. This series of stages is called a life cycle since an offspring passes through the same series before they can produce their own offspring. Therefore, the life cycle is repeated for each generation. The basic stages of a life cycle for all the organisms include a pre-reproductive stage in which the individuals grow and mature and pass through a reproductive stage in which the individuals produce offspring. However, species vary a lot in the particular aspects of their own different life cycles.
Adaptations to Survive
Differences amongst the species in their basic life cycle often reflect adaptations to survive and produce offspring under several different ecological conditions. Consider, for example, some plant species that live in habitats in which they are easily able to grow, mature, and reproduce in one growing season. In the lesser fertile habitats, however, the plants may not grow enough to successfully finish their life cycles in a year. Consequently, the plant species in these habitats can have life cycles with even longer pre-reproductive stages. In addition to being affected by several environmental conditions, life cycles are influenced by the patterns of energy allocation as well. The energy which is used for the growth or the metabolism cannot be used to produce offspring. Therefore, adaptations that increase survival or reproductive success in a life cycle stage can reduce the survival or reproductive success in the other stages. This situation is called a trade-off.
Reproduction
One example of this trade-off is often related to the length of the reproductive stages. The ability to reproduce is the most fundamental part of the life cycle for any living species as it allows that species to multiply and evolve. Reproduction in animals either occurs asexually or with the help of sexual reproduction. Sexual reproduction involves both the male and the female form that particular species. Female animals produce egg cells, which fuses along with a male sperm cell in order to start developing into a new animal. Depending on the place and species, the young will either be looked after by both parents or just by the mother as in the case of mammals. Before an animal can reproduce, it has to find a partner. Animals attract their mates by invariably courting them, a process that varies dramatically among different species. Some species of male birds have brightly coloured feathers and they do elaborate dances in order to try and get the female to notice their features. Other animals, such as certain birds and fish, are known to almost dance together often ending up copying one another. The male animals of many species often have respective features that attract females such as long noses or large manes. Courtship leads to mating among animals in order for reproduction to take place, and these relationships can last for a lifetime or just momentarily for a while. Most classes of animals, which include fish, mammals, reptiles, and birds have simple life cycles. First, they are born, either from their mother or hatched from eggs. Then, they grow and develop into adults. Amphibians and insects have a more complicated life cycle.
Reproductive Stages
Some organisms, including human beings and several perennial plants, have longer reproductive stages. They can reproduce several times during that stage. These kinds of organisms are known to have iteroparous or repeated birth life cycles. In contrast, the salmon and several annual plants are examples of species that have semelparous or single birth life cycles. In this type of life cycle, the individuals reproduce only once and die. Intuitively, iteroparous organisms can be expected to produce more offspring than the semelparous species. However, the semelparous species can be more successful in producing offspring than the iteroparous species, despite the fact that they can only reproduce once. Since semelparous species cannot survive after reproducing, they can allocate all the available energy to produce offspring. Under certain environmental conditions, the extra energy allocation might result in a larger number of offspring than the iteroparous species which has to reserve enough energy for survival too.
List of Life Cycles
A life cycle is a period that involves one generation of an organism by means of reproduction, whether it is through asexual reproduction or sexual reproduction.
There are three kinds of life cycles:
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Haplontic life cycle
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Diplontic life cycle
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Diplobiontic life cycle.
These three types of life cycles feature alternating haploid and diploid phases denoted by n and 2n. The haploid organism becomes a diploid through the process of fertilization that joins the gametes. This results in a zygote that then germinates. To return to the haploid stage, the process of meiosis must occur.
The cycles differ in the product of meiosis, and if mitosis, that is, the growth occurs.
Zygotic and Gametic Meiosis
Zygotic and gametic meiosis contain one mitotic stage and form. During the n phase in the zygotic meiosis and during the 2n phase in the gametic meiosis. Hence, the zygotic and gametic meiosis are collectively termed as haplobiontic, that is, a single mitosis per phase.
Sporic Meiosis
The sporic meiosis, on the other hand, contains two mitosis events, which is, diplobiontic, which, in turn, means one in each phase.