1. Unit Five Ecology and Conservation Biology
Populations of Species

2. Concepts surrounding Evolution
Evolution – the change in the genetic composition of a population over time due to chance alone
Natural Selection – the process by which mutations create certain traits that are more suited to an environment than other traits
Adaptation – individuals that possess those traits that are more suited to the environment survive and generally thrive

3. Concepts surrounding Evolution cont’d
Mutation – a random change in the genetic code (DNA/RNA)
These mutations lead to the development of new traits both helpful and detrimental to a species
Charles Darwin was the first to propose these concepts; voyage of the Beagle in the 1800’s

4. Concepts surrounding Evolution cont’d
Evolution leads to biological diversity
Biodiversity is the variety of life in an ecosystem or defined area
Areas with high biodiversity are called hot spots; these areas are usually in regions with a moderate climate

5. Biodiversity Hot Spots (red)

6. Concepts surrounding Evolution cont’d
Speciation leads to many new species several of which may be wiped out by an extinction event
Extinction causes the disappearance of many species but also allows for the evolution of many new species
Extirpation is the extinction of a species in a specific area
All past mass extinctions were most likely due to catastrophic natural occurrences like Ice ages, meteorites, and volcanic eruptions

7. Levels of Ecological Organization
Ecology – study of the biotic and abiotic factors in an area
Species - organisms that look similar and can breed to produce reproductively capable offspring
Population – a group of individuals of the same species living together
Community - several populations that live in the same area

8. Levels of Ecological Organization cont’d
Ecosystem – a defined area with a specific set of biotic and abiotic factors; usually defined by vegetative associations
Speciation is demonstrated by using a Phylogenetic Tree
Habitat versus Niche – habitat is where an organism lives a niche is how an organism lives in its habitat

9. Levels of Ecological Organization cont’d
Specialist versus Generalist - a specialist requires a specific set of resources whereas a generalist can live off a broader range of resources
Example: Scrub Jay and Raccoon

10. Population Ecology
Population Ecology – study of the dynamics of populations such as density, distribution, sex ratio, age structure, and mortality/natality
Population density – how many individuals there are of a species per unit area
Population distribution - spatial arrangement of individuals within an area

11. Population Ecology cont’d
Survivorship curves – show the distribution of ages across a population; predicts the likelihood of death at various ages per species

12. Population Ecology cont’d
Immigration versus Emigration
How many enter an area versus how many leave an area
Formula for Growth Rate
(Birth Rate + Immigration Rate) –
(Death Rate + Emigration Rate) = Growth rate

13. Population Ecology cont’d
Exponential Growth – the global human population began to increase exponentially at onset of the Industrial Revolution
However, now there is a population paradox globally

14. Population Ecology cont’d
Population growth is dependent on biotic potential
Some species can reproduce many offspring per reproductive event, and can have several reproductive events per year
Those species that fit into the above-mentioned category are “r – selected”: mice and rabbits
Species that seldom reproduce, and when they do reproduce only have one or two offspring are “k-selected”: whales and humans

15. Population Ecology cont’d
Limiting Factor – a resource that prevents a population from increasing in size
Carrying Capacity – total number of individuals an ecosystem can sustain based on resource availability
Limiting factors can vary from ecosystem to ecosystem and populations of different species can vary in size within the same ecosystem
What are some examples of limiting factors?