4.1 Population Ecology I

Which of the issues below could influence the future population of a species of toads introduced to Australia?

A. Presence of predators

B. Climate events including drought

C. Availability of food resources

D. Presence of disease

all of the above

What is the change in the population? In a population with 100 toads, researchers found that in the year of the study, 20 new babies survived while 10 older toads died. 15 new toads immigrated into the population, but 8 toads emigrated out of the population. What is the change in population, N?

+17%

what is Population ecology?

The study of how populations of organisms change over time and space. It examines how populations interact with the environment and with each other.

How does population size increase or decrease?

• births +

• deaths -

• emigration -

• immigration +

You are a wildlife manager studying Australian Cane Toads. In 2020 you record 33 births, 54 deaths, 23 immigrants, and 34 emigrants. This population is:

decreasing

How to design a model that predicts the growth of a population?

we need to specify the relevant time interval. This interval should make sense for the species. For bacteria, the interval could be an hour. For other organisms, a much longer interval makes sense.

model population growth equation

what are the three patterns in population growth

1. The population grows whenever birth rates exceed death rates (b > d).

2. The population shrinks whenever the death rate exceeds the birth rate (d > b).

3. The population remains constant whenever the birth rate equals death (b = d).

what is the intrinsic rate of increase or rate of change

represented by r; represents the difference between birth and death rates to easily predict which pattern will emerge

On a research trip to Australia, you are attempting to study the spread of Cane Toads. You find that there are in fact two groups – one found in Northern Australia (mostly in Queensland) and a newer undocumented group that was recently found near Perth (in the Southwest). These two groups are separated by hundreds of miles of desert – likely limiting dispersal for this aquatic species. These 2 groups represent a single population. True or False

FALSE

What is a population?

• A group of individuals that can interbreed

• Living in the same place at the same time

Which feature of a population is characterized by the spread or distribution of its members?

range and maybe density

what are the key features of a population?

• density- 200 million individuals/ 1.2 million square kilometers = 167 toad/ square kilometer

• size- The size of the Australian Cane Toad Population is estimated to be over 200 million individuals.

• range-Their range is approximately 1.2 million square kilometers (an area slightly larger than the states of Texas and Oklahoma combined

What is Ecology?

The study of the relationships of organisms to one another and to their environment.

• population ecology…