Today we will be learning about the two forms of fertilization: Internal and External:

Directions: Have one person read the passage below out loud. Then create a venn diagram comparing and contrasting internal vs external fertilization. Also brainstorm with your group, the pros and cons of each type of fertilization.  

Fertilization is the process by which sperm and egg cells unite to form a new organism. In the animal kingdom, this process occurs in two main ways: internal fertilization and external fertilization. Each method has its own advantages and disadvantages, affecting the survival and development of offspring.

Internal fertilization occurs inside the body of the female and is common in mammals, birds, reptiles, and some fish. During this process, the male deposits sperm directly into the female’s reproductive system, where it can meet the egg. One advantage of internal fertilization is that it provides protection from the environment. Since fertilization happens inside the body, developing embryos are shielded from harsh conditions such as temperature changes, predators, and diseases. Additionally, this method often leads to higher survival rates for embryos because sperm and eggs are not exposed to external threats. Internal fertilization also allows for a more efficient use of energy since fewer offspring are produced, but each one has a higher chance of surviving. However, there are also drawbacks. Organisms that use internal fertilization typically produce fewer offspring because the process requires more energy and parental care. Finding a mate can also be challenging, as it often involves specific behaviors or adaptations to attract a partner.

In contrast, external fertilization occurs outside the body, usually in water, and is used by many fish, amphibians, and aquatic invertebrates. During this process, females release eggs into the water, and males release sperm over the eggs. One major advantage of external fertilization is the ability to produce large numbers of offspring. Since environmental risks are high, releasing many eggs and sperm increases the chances that some will survive to adulthood. Additionally, organisms that use external fertilization do not need to invest as much energy into each individual offspring or in providing parental care, allowing them to focus on producing vast quantities of eggs and sperm. However, this method also comes with significant risks. Since eggs and sperm are exposed to predators, environmental conditions, and the risk of not meeting each other, many do not survive. Even if fertilization is successful, the exposed embryos face threats from predators and environmental changes, leading to lower survival rates.

Both methods of fertilization have evolved to suit the needs of different species. Internal fertilization is more energy-intensive but offers higher protection and survival chances for each individual offspring. External fertilization, on the other hand, relies on producing large numbers of offspring to offset the risks posed by the environment. Understanding these methods helps us appreciate the diverse strategies life has developed to continue thriving on Earth.

Directions: 

Read the article and watch the video (in the webpage). 

Stop reading when you get to the embryonic stage.