External Fertilization and Distribution of Life in Organisms
Melting male gamete (sperm) and female gamete (ovum) cells that occur outside the body. Male animals will stimulate female animals to spray the ovum, while male animals will release sperm cells in a watery region. Water media is needed to relax the meeting of these two gamete cells. Therefore, this type of fusion usually occurs in animals in the aquatic environment, such as fish and frogs. In addition, the watery area will protect the embryo eggs during their development, this is because the embryo eggs that are formed do not have a shell and require high levels of humidity.
If the eggs are moved to a dry area (land), these eggs will dry out and will damage the development of the embryo. In some aquatic animals, eggs will develop into ciliated larval forms that will wander attached to the bottom of the water to form a new colony, or sessile phase (attached to the bottom of the water) for vegetative development. Examples are found in sponges, jellyfish, etc.
Also Read Articles That May Be Associated: Understanding, and Characteristics of Dicotyledon Plants and Examples in Complete
Distribution of Life in Organisms
Definition of Life Distribution
Dispersal or distribution of life is a component of population dynamics that ensures long-term survival of populations and animal species. Dispersal is the movement of animals from their birthplace to new areas to live and reproduce. Displacement in dispersal is one-way without traveling back to its original place. The movement of animals back to their original place is called migration (Nybakken, 1988).
Every organism in its habitat is always influenced by various things around it. Each factor that influences the life of the organism is called an environmental factor. Environment has dimensions of space and time, which means that environmental conditions cannot be uniform both in terms of space and time. Environmental conditions will change with changing space, and will change with time.
According to Mc Naughton and Wolf (1992) each ecosystem has different characteristics, due to its species composition, community and organism distribution. Distribution in the pattern of space and time has two basic meanings, which are the result of the response of organisms with their adaptation to environmental heterogeneity in space and time and the organisms themselves act as modifiers or modify environmental heterogeneity.
Distribution patterns of living things in time
Most organisms are spread out at several stages of their life cycle. They leave their home environment both permanently and seasonally for more suitable habitat. This movement is very important for the survival of individuals, especially young people, who are the most vulnerable groups to spread, because there is no room for all in their home environment (Backus, 1986).
Migration movements are divided into three categories, the most common is the repetition of the journey made by individuals. Such as daily or annual migration, short term or long term. Zooplankton in the ocean moves downward into deeper areas throughout the day and moves to the surface at night. This movement appears in response to the intensity of light. Earthworms annually migrate deeper into the soil to spend the winter and return to the surface in the fall and summer.
The second type of migration is only one return trip. Such migrations are common to some Pacific salmon species. Salmon hatch in the sea then migrate to the river, then grow to adulthood and return to the sea to reproduce and then die.
The third type of migration, for example in monarch butterflies, migrates and does not return north but the offspring return to their original place. About 70% of the last generation of monarch butterflies in the summer moves south to winter in the highlands of Mexico, this journey crosses about 14000 km. From winter moving in January and arriving in the depths of southern America early in the fall they start for a new generation (Sugianto, 1994).