Understanding Populations

How Populations Change in Size Objectives 1. Describe the three main properties of a population. 2. Describe exponential population growth. 3. Describe how the reproductive behavior of individuals can affect the growth rate of their population. 4. Explain how population sizes in nature are regulated.

What is a population? All members of a species living in the same place at the same time Properties of Populations Density – the number of individuals per unit area or volume

Dispersion – the relative distribution or arrangement of its individuals within a given amount of space Size – actual number of individuals

How does a population grow More births than deaths Growth rate – change in pop. Over time Change in pop. Size = births - deaths

How fast can a population grow Reproductive potential – the max number of offspring that each member of a population can produce

Most organisms have a high reproductive potential because few offspring actually survive

Potential increases when individuals produce more offspring at a time, more often, and reproduction early (shortens generation time – ave. time it takes to reach reproductive age)

Small animals usually have a shorter generation time than larger animals

Exponential Growth As a population grows, it grows faster Occurs in nature when populations have plenty of food and space and no competition

What limits population growth Carrying capacity - max pop. That the ecosystem can support indefinitely Amount of resources – limited resources determines carrying capacity

Competition within a population Territory Food mates

Types of population regulation Density dependent – density, of individuals affects growth’ all individuals are affected diseases

Density independent – certain portions of the pop Density independent – certain portions of the pop. May die regardless of the pop. Density Severe weather, natural disasters

How Species Interact Objectives 1. Explain the difference between niche and habitat. 2. Give examples of parts of a niche. 3. Describe the five major types of interactions between species. 4. Explain the difference between parasitism and predation. 5. Explain how symbiotic relationships may evolve.

Organism’s niche Unique role of a species within an ecosystem or a pattern of use of its habitat or it’s “job” Includes physical home, environmental factors necessary for survival, and all interactions

Ways species interact Competition – both harmful Relationship in which different individuals or population attempt to use the same limited resource

Within and between species Between different species it’s called overlap

Competition is reduced by Indirect competition – when species do not come into contact with each other Competition is reduced by Evolution – better adaptations Divide niche in time and space

Predation – 1 benefits and the other is harmed Populations of predators depend on populations of prey

Adaptations to avoid predators Camouflage used to lie and wait or hide Warning coloration Mimicry Protective covering

Parasitism – 1 benefits, other is harmed or killed Parasite (flees, ticks, tape and heartworms, leaches, mistletoe Host

Mutualism – both benefit Bees and flowers Commensalism – 1 benefits, the other is unaffected “hitchhikers”, birds and trees

Symbiosis – close relationship coevolution