Unit Five Ecology and Conservation Biology Populations of Species

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

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

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

Biodiversity Hot Spots (red)

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

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

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

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

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

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

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

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

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

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?