Download Section 4.1 Population Dynamics pg.91

Section 4.1 Population Dynamics pg.91-99
Chase Upshaw
Principles of Population Growth
A population is a group of organisms, all of the same species, that live in a
specific area
Scientists study changes in populations in a variety of ways
Ex. Introducing organisms into a controlled environment with abundant
resources; observe how the organisms react
How fast do populations grow?
Starts out slowly then increases rapidly; resembles a J shape on a chart of
population growth
Starts out small because the number of individuals reproducing is small
Then, the numbers become larger over time after constant reproduction
Is growth unlimited?
Exponential growth- means that as a population gets larger, it also
grows at a faster rate
Results in unchecked growth
What can limit growth?
Population growth does have limits
Limiting factors such as availability of food, disease, predators, or lack of
space, will cause growth to slow
Creates a S-shaped growth curve
Carrying capacity
Carrying capacity- the number of organisms of one species that an
environment can support indefinitely
When a population is developing in an environment with resources, there are
more births than deaths and the population increases until the carrying
capacity is reached or passed
When carrying capacity is overshot, limiting factors come into place
Fluctuating line on a graph of population growth
Reproduction Patterns
Life-history pattern- an organism’s reproductive pattern
Slow life-history pattern- slow rate of reproduction; few offspring
Rapid life-history pattern- rapid reproduction; many offspring in a short
period of time
Rapid life-history patterns
Common in organisms from changeable or unpredictable environments
Characteristics of rapid life-history pattern organisms
Small body size
Mature rapidly
Reproduce early
Short life span
Populations increase rapidly and are easily affected by environmental
changes
Slow life-history patterns
Characteristics of slow life-history pattern organisms
Larger species
Live in more stable environments
Reproduce and mature slowly
Long life expectancy
Density factors and population growth
Dispersal of organisms: random, clumped, and uniform can determine limiting
factors
Density-dependent factor- limiting factors such as disease, parasites,
or food availability that affect growth of a population
Density-independent factor- factor such as temperature, storms, floods,
drought, or habitat disruption that affects all populations, regardless of
their density
Organism Interactions Limit Population Size
Population sizes are not only limited by abiotic factors, but by biotic factors
too
Predation affects population size
When a predator consumes prey on a large enough scale, it can have a drastic
effect on the size of the prey population
Populations of predators and their prey are known to experience cycles or
changes in their numbers over periods of time
Ex. Hare and Lynx
In prey populations, usually the young, old, and injured organisms are caught
Competition within a population
Competition is a density-dependent factor
When only few individuals compete for resources no problem arises
When the demand of resources exceeds supply, then competition increases
and population size decreases
The effects of crowding and stress
When an environment becomes crowded, organisms may exhibit symptoms of
stress
Symptoms include:
Aggression
Decrease in parental care
Decreased fertility
Decreased resistance to disease
Section 4.2 Human Population pg.100-103
Chase Upshaw
World Population
Census is taken every ten years in the United States
Provides a picture of how many people there are in the United States, their
economic condition, and where they live
The United Nations Population Division tracks similar information on all the
countries of the world
Demography- the study of human population size, the density and
distribution, movement, and its birth and death rates
Human population growth
Human population growth is the result of humans consciously changing their
environment
As a result, humans live longer and are able to produce offspring that live
long enough to produce offspring, hence, a population grows
Calculating growth rate
Birthrate- the number of live births per 1000 population in a given year
Death rate- the number of deaths per 1000 population in a given year
(Birthrate + Immigration rate) – (Death rate + Emigration rate) = Population
Growth Rate
Birthrate – Death rate = Population Growth Rate
Doubling time
Doubling time- the time needed for a population to double in size
Depends on the current size of the population and the growth rate
Age structure
Age structure- refers to the proportions of the population that are in
different age levels
Age structure info is used to determine how fast a population will increase
or grow
Ecology and growth
Some countries are concerned with providing the most basic needs
Other countries worry about maintaining healthy conditions that are already
present and providing luxuries
Section 5.1 Vanishing Species pg.111-120
Chase Upshaw
Biological Diversity
Biodiversity- refers to the variety of species in a specific area
The simplest and most common measure of biodiversity is the number of
different species that live in a certain area
Where is biodiversity found?
Biodiversity increases as you move toward the equator
Tropical regions contain 2/3 of all land species on Earth
Richest environments for biodiversity are usually the warmest places
Studying biodiversity
Study of islands in 1960; testing the development of biodiversity on islands
Used islands off the coast of Florida
Removed the organisms and observed which ones came back first
Importance of Biodiversity
You might go to a place in nature to relax, think, or get inspiration for songs,
paintings, photographs, and literature
Importance to nature
All living things are interdependent; they rely on others to survive
The loss of a population may greatly affect the entire ecosystem
Biodiversity brings stability
Ecosystems are stable if their biodiversity is maintained
A change in species can destabilize
More difficult for disease to spread
Importance to people
Humans depend on other organisms for their needs
Plants for oxygen and food
Animals for food
Biodiversity could help breeders produce additional food crops
Cross breeding to get the best characteristics
Maintain health of humans
Penicillium bacteria is used to make penicillin
Loss of Biodiversity
Extinction- the disappearance of a species when the last of its members
dies
Background extinction is responsible for 1 out of every 1,000,000
extinctions, but the regular extinction rate is higher than that
Extinction is due to:
Expanding human population
Habitat loss
Land exploitation
Endangered species- when a species numbers become so low that
extinction is possible
Threatened species- when the population of a species is likely to become
endangered
Threats to Biodiversity
Changes to habitats can threaten organisms with extinction
Habitat loss
One of the biggest reasons for decline of biodiversity is habitat loss
The soil in the Amazon has very little nutrient supply
Coral reefs are similar to tropical rain forests in biodiversity
Habitat fragmentation
Habitat fragmentation- the separation of wilderness areas from other
wilderness areas
Can contribute to:
Increased extinction of local species
Disruption of ecological processes
New opportunities for invasions by introduced or exotic species
Increased risk of fire
Change in local climate
Decreases biodiversity
Edge Effect
The edge of a habitat or ecosystem is where one habitat or ecosystem
meets another
Edge effect- the different conditions along the boundaries of an
ecosystem
Greater biodiversity because different habitats with different species are
brought together
Animals are brought together
Habitat degradation
Habitat degradation- the damage to a habitat by pollution
Three types of pollution- air, water, and land pollution
Acid precipitation- rain, snow, sleet, and fog with low pH values or
levels
Water vapor combines with air pollution to form acid precipitation
Ozone layer- the region that absorbs some of the ultraviolet waves
striking the atmosphere reducing the ultraviolet radiation reaching the
Earth’s surface
Water pollution
Degrades aquatic habitats in streams, rivers, lakes, and oceans
Detergents, heavy metals, and industrial chemicals in runoff affect aquatic
habitats; excess fertilizers and animal wastes can also have an impact in
degrading aquatic habitats
Land pollution
The average person produces about 1.8 kg of solid waste daily and about 657
kg each year
Hard to decompose wastes in landfills are an example of pollution
Pesticides on crops is another example of land pollution
Exotic species
People sometimes introduce a new species into an ecosystem, either
intentionally or unintentionally
These species are called exotic species
They can cause problems for the native species in the area
Exotic species- nonnative species in an area; may take over niches of
native species in an area and eventually replace them
Section 5.2 Conservation of Biodiversity pg.121-125
Conservation Biology
Conservation biology- the study and implementation of methods to
protect biodiversity
Strategies are based on principles of ecology
Includes natural resource conservation and species conservation; even
soil
Natural resources are those parts of the environment that are useful or
necessary for living organisms
Includes sunlight, water, air, and plant and animal resources
Legal protections of species
The U.S. Endangered Species Act became law in 1973, in response to concern
about species extinction
The law made it illegal to harm any species on the endangered or threatened
species lists and for federal agencies to fund any project that would harm
organisms on these lists
The Convention on International Trade in Endangered Species has
established lists of species for which international trade is prohibited
Preserving habitats
Creation of natural preserves and parks
First U.S. national park, Yellowstone, was established in 1872
Protects the environment and provides habitats for many organisms
Habitat corridors
Best strategy is to protect the largest area possible
Habitat corridors- protected strips of land that allow the migration of
organisms from one wilderness area to another
Working with people
Rangers manage national parks and ensure the protection of organisms
Sustainable use- a philosophy that strives to enable people to use
natural resources in ways that will benefit them and maintain the
ecosystem
Reintroduction and species preservation programs
Reintroduction programs- programs that release organisms into an area
where their species once lived in hopes of reestablishing naturally
reproducing populations
Most successful reintroductions occur when organisms are taken from an
area in the wild and transported to a new suitable habitat
Captivity
Some species no longer exist in the wild, but a small number of individual
organisms are maintained by humans
Captivity- an organism that is held by people
Protecting plant species
Best way to protect a plant species is to allow it to exist in a natural
ecosystem
Another way is storing the seeds in seed banks
Reintroductions of captive animals is more difficult than the reintroductions
of plants
Keeping animals in captivity, with enough space, adequate care, and proper
food is expensive
Animals kept in captivity may lose the necessary behaviors to survive and
reproduce in the wild