What is a Population? All the members of a species living in the same place at the same time. Examples: Palm trees on an island, a school of specific fish, daisies in a field in Ohio.

Properties of Populations Population density- the number of individuals per unit area or volume Example: the number of small mouth bass per cubic meter of water in a lake.

Properties of Populations Dispersion- the relative distribution or arrangement of its individuals within a given amount of space. Even Random Clumped

Population Dispersion

How Does a Population Grow? Growth Rate- the birth rate minus the death rate of a population. Change in population size = Births - Deaths

How Fast Can a Population Grow? Biotic potential: The fastest rate at which its potential population can grow.

How Fast Can A Population Grow? Reproductive Potential: The maximum number of offspring that each member of the population can produce.

Reproductive Potential If perfect conditions, it would take a pair of elephants 750 years to produce 19 million descendents.

Reproductive Potential-Exponential A bacteria cell could produce 19 million new cells in a few days or weeks.

Bacterial growth is an example of exponential growth.

Carrying Capacity Carrying capacity is the maximum population that the ecosystem can support indefinitely.

Carrying Capacity While a population may increase beyond this number, it will not remain at this increased size. Example: Rabbits in Australia demonstrate exponential growth and carrying capacity. Originally there were no rabbits in Australia. When they were introduced in 1859, their numbers grew rapidly because they had plenty of vegetation, no competition, and no predators. Eventually, disease and starvation caused the rabbit population to crash.

Carrying Capacity Over time, the vegetation recovered, and the rabbit population began to increase again. The increasing and decreasing cycle continues, though less dramatically, as the population stays closer to the carrying capacity over time.

Resource Limits A species reaches its carrying capacity when it consumes a particular natural resource at the same rate at which the ecosystem produces the resource. That natural resource is called a limiting factor. For example, plant growth is limited by supplies of water, sunlight, and mineral nutrients. The supply of the most severely limited resources determines the current carrying capacity.

Types of Population Regulation Density dependent regulation Deaths occur more quickly in a crowded population than in a sparse population. Reasons for deaths- Competition Predation Disease

Types of Population Regulation Density Independent Regulation When certain portions of the population die regardless of how dense the population is. Reasons for deaths: Weather Natural disasters Human actions (deforestation, damming a river, hunting, etc.)

Niche Niche: the unique role of a species in an ecosystem It includes the species’: Physical home (habitat). Environmental factors needed for survival. All interactions with other organisms. Its functional role- what does it do? How it uses its habitat. Copy all of this slide!

Example of a Niche Kangaroos Kangaroos occupy Australia’s niche of large grazing (feeding on grasses) herbivores Copy all of this slide!

Predation An organism that feeds on another organism is called a predator. The organism that is fed upon is the prey. Examples: Snakes eating mice. Bats eating insects. Whales consuming krill.

Predation Some predators eat only specific types of prey. In this type of relationship, the sizes of each population tend to increase and decrease in linked patterns.

Predation

Competition Competition is a relationship in which different individuals or populations attempt to use the same limited resource. Each individual has less access to the resource and so is harmed by the competition. Competition can occur both within and between species.

Competition Indirect competition occurs when species never come in contact with each other. Examples: If one species feeds on a certain plant during the day and another species feeds on the same plant at night. Humans rarely interact with the insects that eat our food crops, but the insects are still competing with us for food.

Competition

Symbiosis The close association between two or more organisms of different species Three types of symbiosis: Mutualism Commensalism Parasitism

Mutualism A symbiotic relationship between two organisms of different species in which each member benefits.

Examples of Mutualism Tickbirds perched on a black rhinoceros get food (pests on rhinos) and help the rhino get rid of pests

More Examples of Mutualism One kind of flagellate lives in the guts of termites and digests the cellulose in the wood that the termites eat. Without the protozoa, the termites could not completely digest the cellulose.

More Examples of Mutualism Some types of fungi grow on the roots of plants and release an acid that changes minerals in the soil into forms that plants can use.

More Examples of Mutualism You and a species of bacteria that lives in your intestines benefit each other! The bacteria get a plentiful food supply from you and in return you get vitamins that the bacteria produce.

More Mutualism Examples The living corals near the surface of the water provide a home for the algae. The algae produce food through photosynthesis that is used by the corals.

Mutualism

Commensalism A symbiotic relationship between two organisms of different species in which one organism benefits without harming the other organism

Examples of Commensalism Barnacles attached to a gray whale gain a home and transportation to areas with food while leaving the whale unaffected.

Examples of Commensalism Remoras hitch a ride and feed on scraps of food left by sharks. The remoras benefit from this relationship while sharks are unaffected.

Examples of Commensalism The Cattle Egret (Bubulcus ibis) is often found in pastures following horses and cattle. As the livestock graze, insects are stirred up by their movement and this provides food for the egrets.

More Examples of Commensalism The Great Burdock (Arctium lappa) has spines on its seeds that curve upward which allow the seeds to attach themselves to the fur of passing animals. The plant benefits by having its seeds dispersed in a large area and the animals are not affected.

More Examples of Commensalism Orchids receive more sunlight for photosynthesis if they grow high on tree branches. The orchid plants are helped by the tree. The tree gets nothing in return from the orchids.

Commensalism

Parasitism A symbiotic relationship between two organisms of different species in which one organism benefits and the other is harmed. The organism that benefits is called the parasite. The organism that is harmed is called the host.

Parasitism The parasite gets nourishment from its host, which is weakened in the process. Sometimes a host organism becomes so weak that it dies. Some parasites, such as ticks, live outside the host’s body. Other parasites, such as tapeworms, live inside the host’s body.

Examples of Parasitism The flagellate parasite, Giardia Lamblia, lives in the digestive tracts of humans and other vertebrates causing diarrhea and severe stomach cramps. Giardia live in water and sometimes hikers drink infected water.

More Examples of Parasitism A louse on a human scalp receives nourishment from drinking the human’s blood and also causes a rash or irritation.

More Examples of Parasitism A female wasp lays eggs in a caterpillar. When the eggs hatch, the wasps eat the caterpillar alive!

More Examples of Parasitism A flea uses the blood of a rabbit for nourishment.

More Examples of Parasitism Lampreys attach to fish causing sores.

Parasitism