Unit 4 Lesson 10: Ecosystem Interactions Flashcards
natality
birth
immigration
the movement of individuals into an area
emigration
the movement of individuals out of an area
The table below shows all four factors that can change the size of a population. It is important to remember that populations usually remain relatively stable, or at least return to stable conditions when the environment returns to normal.
Natality (birth): Increase
Mortality (death): Decrease
Immigration (joining a population): Increase
Emigration (leaving a population): Decrease
Immigration and emigration are related to the available resources found in an ecosystem (the living and nonliving parts of an area). Elaborate
If there are too many individuals in the population (all members of the same species in the same area) to be supported by the amount of food, space, and water, then some individuals may leave the population to search for resources elsewhere. As they travel, they may come across another population in a different area where the resources are not limited. Those individuals may join this new population, assuming the environment can support all of them.
Scientists have created a mathematical model used to calculate the change in the size of a population. This model is represented with the equation
Population change =(Natality−Mortality)+(Immigration−Emigration)
What does this equation mean Population change =(Natality−Mortality)+(Immigration−Emigration)
This means that the number of individuals born minus those that died is added to those that come into the population minus those that leave. If the value is negative, then the population is getting smaller. If the value is positive, then the population is getting larger.
Within a population, the traits individuals receive from their parents can differ. Scientists call those differences
genetic variation
. The process that “selects” one version of a trait over another to survive is called
natural selection
. To work, natural selection requires two things:
genetic variation in traits, and environmental conditions that make one version of the trait more advantageous for survival than the other.
genetic variation benefits
Some genetic variation in traits can make some individuals in the population better at competing for resources, like food, water, habitats, and mates.
There are two main types of competition in an ecosystem and both types are dependent on the degree of biodiversity in that ecosystem. The first, called interspecific competition whats that
competition for limited resources that occurs between individuals of different species
Will genetic varitaion and natrual slection always be helpful
Keep in mind that the environment changes, so just because a trait may be advantageous at one time, that may not always be the case.
Example of interspecific competition
On the floor of the tropical rainforest, very little light reaches the ground, so plants need to bend and grow in ways that will allow them to collect as much light as possible. To do this, they have adapted very large, broad leaves. Those species with really large leaves will be better at collecting light than other species with smaller leaves, so they will grow better. The species with larger leaves will out compete the species with smaller leaves.
The other type of competition is called intraspecific competition whats that
competition for limited resources that occurs between individuals within the same species
Example of intraspecific competition
For example, the male weaverbird builds a very elaborate nest with the hope of attracting a female. Several males each build their nests in the same area of trees and do a mating dance to get the attention of the female. When she arrives, she examines all of the nests and then selects the male that built the best one (in her opinion). She mates with him and lays her eggs in his nest. The other males are out of luck here. They were in competition with each other for the female’s attention, but only one was successful.
Another way population sizes are regulated is through predator/prey interactions. What would be like if there were no predators
Without predators, the prey species populations would increase dramatically. This boom in population size would put a huge strain on resources, and ultimately, the prey species would die off because they had used up all of the resources. Both predator and prey populations usually remain stable as long as resources are available to support their populations.
Other things that can alter the size of population are the seasonal changes in the environment.
Almost all ecosystems undergo at least some form of seasonal weather change—such as rainy season, freezing temperatures, flooding, drought, etc. These weather and climate conditions can alter how many members of the population are alive at any given point.
In latitudes closer to the poles, winter produces freezing and below-freezing temperatures.
Plants and most animals cannot tolerate these, so they either die back (in the case of plants), hibernate, or migrate (in the case of animals). Those animals that eat plants during the winter (like rabbits) show a decrease in population sizes over the winter months because there is not enough food to eat. The lack of resources keeps the population in check until spring, when there will be enough food for more rabbits to survive.
What happens to the population size of a species if it has all the resources it needs? Think immediate and long-term.
In the immediate term, the population of the organisms would increase dramatically. This is because they have all of the resources they would need to survive and reproduce. The carrying capacity of the environment would be very large. However, in the long term, it is unlikely those vast resources will last forever. As they start to dwindle, the number of individuals able to be supported by the environment would decrease. This would result in a decrease in population size.
How can seasonal weather changes impact population sizes of plants?
Most plants are unable to tolerate living when it is very cold. As such, they die back or become dormant (in the case of perennials). This reduces their population size for the winter. Annuals (plants that grow new every year) start to sprout when the weather gets warmer, increasing their population size.
What would be part of a coral reef community?
A community is all of the living things in a given area. In a coral reef community, this would include the corals, shrimp, fish of all sizes, sea stars, algae, isopods, and every other living thing surviving on the reef.
How does immigration compare with emigration?
Immigration involves organisms moving into an area, while emigration involves organisms leaving.
What is the explanation for why competition limits population size?
When resources are limited, individuals have to compete for them. This could be for space, food, light, or mates. Not all individuals are going to survive because more are born than the environment can support. Those that are best suited for the environment will survive to reproduce, while others will perish. Competing against each other limits the population size because the winner survives, while the loser dies.
Hibernation is often referred to as a long winter’s nap, but it is much more complicated. Depending on the species, some animals den up alone in a protected space while others treat hibernation as a group activity. What is state of torpor
The animals are able to enter a state of torpor, where they lower their metabolic rate, body temperature, heart rate, and even their breathing to reduce their need for food.
Species that remain in these torpor states for more than twenty-four hours are
hibernating
The duration of hibernation periods varies and is highly dependent on local
weather condition
Some animals, like snails, will follow these same procedures during periods of extreme heat as well as extreme cold; in times of extreme heat this is known as
aestivation
Are brear really hiberanting throughout the iwinter
While bears are thought to hibernate for the winter, individuals will often wake on warmer days and leave their dens for water or a walkabout, and then return to their den that evening.
While many plants do die off with freezing temperatures, others have evolved to survive the winter weather.
Trees and shrubs drain their food supply from their leaves into their trunks, stems, and roots.
As the weather gets even colder many trees and shrubs go through a process where the visible chlorophyll is drained and the carotenoids and anthocyanins take over. What this this cause
These chemicals cause the yellow, orange, red, pink, and purple leaf colors of fall.
As the weather gets even colder many trees and shrubs go through a process where
the visible chlorophyll is drained and the carotenoids and anthocyanins take over.
What do other plants do during winter dormancy
Other plants simply sacrifice their above-ground leaves and stems and, storing their food supply in their crown and roots, enter a period of winter dormancy.
