Fertilization

Definition

Fertilization is the biological process where male and female gametes unite to form a zygote, initiating the development of a new organism. This event is crucial in both plant and animal reproduction as it leads to genetic diversity and the continuation of species. In plants, fertilization often occurs after pollination, while in animals, it usually takes place within the reproductive tract of the female, setting the stage for subsequent developmental processes.

5 Must Know Facts For Your Next Test

1. In flowering plants, fertilization occurs after successful pollination, where pollen grains grow a tube to reach the ovule inside the ovary.
2. In many animals, fertilization can be external or internal; for example, fish often fertilize eggs outside their bodies, while mammals typically do so internally.
3. Double fertilization is a unique feature of angiosperms (flowering plants) where one sperm fertilizes the egg and another sperm fuses with two polar nuclei to form the triploid endosperm.
4. Fertilization restores the diploid chromosome number in organisms by combining haploid gametes, thus ensuring genetic diversity in offspring.
5. The timing and conditions for fertilization are crucial; for instance, many animals have specific mating seasons that coincide with environmental conditions favorable for the survival of offspring.

Review Questions

• Explain how fertilization contributes to genetic diversity in plant and animal species.
  • Fertilization brings together genetic material from two distinct parents, resulting in offspring that have a unique combination of genes. In plants, this occurs when pollen from one flower fertilizes the ovule of another, leading to variation within a population. In animals, the fusion of sperm and egg also combines different alleles, enhancing genetic variability which is essential for adaptation and evolution.
• Compare and contrast external and internal fertilization in animals, including advantages and disadvantages of each method.
  • External fertilization involves the release of gametes into the environment, commonly seen in aquatic species like fish. Its advantage is producing numerous offspring quickly; however, it also leads to higher mortality rates due to predation. In contrast, internal fertilization occurs within the female’s reproductive tract and usually results in fewer but more viable offspring due to protection during development. This method increases chances for survival but requires more complex mating behaviors.
• Evaluate the significance of double fertilization in flowering plants and its impact on plant evolution.
  • Double fertilization is significant because it leads to both the formation of a zygote and a triploid endosperm that nourishes the developing embryo. This process allows flowering plants to optimize resources for seed development, enhancing survival rates for seeds. The ability to produce seeds with stored nutrients has likely contributed to the evolutionary success and diversification of angiosperms compared to other plant groups.

Related terms

Gamete: A reproductive cell that carries half the genetic material required to form a new organism; in animals, these are sperm and eggs, while in plants, they are pollen and ovules.

Zygote:

The initial cell formed when a sperm cell fertilizes an egg cell, which then undergoes mitotic divisions to develop into an embryo.

Pollination: The transfer of pollen from the male anther to the female stigma of flowers, which often precedes fertilization in flowering plants.