A population or group of populations, whose members share common characteristics. They can breed with one another and produce fertile offspring
Genetic change in populations over time. Genetic change leads to changes in appearance, functioning or behavior over generations
Traits that enhance survival and reproduction. These traits are past on more frequently to future generations that those traits that do not aid in survival and reproduction.
What did Charles Darwin and Alfred Wallace propose in 1858?
They proposed natural selection as the mechanism of evolution
The process where, over time, characteristics that lead to better reproductive success will evolve in the population
Natural Selection changes characteristics through:
-Directional Selection, which drives a feature in one direction.
- Stabilizing Selection, which favors intermediate traits.
- Disruptive Selection, which traits diverge in two or more directions.
Unrelated species may evolve similar traits because they live in similar environments.
Biological Diversity (Biodiversity)
The variety of life across all levels of biological organization:
Species formation due to physical separation of populations. This is the main mode of speciation.
Species form populations that become reproductively isolated within the same area.
- Feed in different areas
- Mate in different seasons
- Hybridization between two species
Phylogenetic Trees (cladograms)
Show relationships among species, groups, and genes. Scientists can trace how certain traits evolved.
Extinction is a natural process, BUT...
...humans profoundly affect rates of extinction and biodiversity loss affects people directly.
When does extinction occur?
When the environment changes rapidly and Natural Selection cannot keep up.
Name a few more causes of Extinction
- Severe weather, climate change, changing in sea levels
- New species, small populations
- Specialized species
How are we causing the 6th mass extinction event?
- Resource depletion, population growth, development
- Destruction of natural habitats
Investigates the dynamics of population change and the factors affecting the distribution and abundance of members of a population and why some populations increase and others decrease.
Studies living and nonliving components of systems to reveal patterns and to see how nutrient and energy flows.
An organism's use of resources. This term can also refer to the organism's functional role in a community, it's habitat use, food selection, role in energy and nutrient flow, and interactions with other individuals.
Have narrow niches and specific needs. Extremely good at what they do, but vulnerable when conditions change.
Species with broad niches. They use a wide array of habitats and resources and can live in many different places.
Number of individuals in a population per unit area.
There are "low" and "high" densities
For large organisms, who need many resources and a large area to survive. It is more difficult to find a mate with less organisms due to lack of space which is caused my the size of the organisms.
Easier to find mates, but there is an increase in competition and vulnerability to predation. There is also an increased transmission of diseases.
Population Distribution (dispersion)
Special arrangement of organisms:
- Random Distribution
- Uniform Distribution
- Clumped Distribution
Individuals evenly spaced. This distribution includes territoriality and competition.
Arranged according to availability of resources. This distribution is the most common in nature.
Age Distribution (structure)
the relative numbers of organisms of each age in a population. Displayed in an "Age Structure diagram" (pyramid).
the likelihood of death varies with age
Type I: more deaths at older ages
Type II: Equal number of deaths at all ages
Type III:more deaths at younger ages
A populations increases by a fixed percent. Graph has a J-curve. It occurs in nature due to small population, low competition, and ideal conditions.
physical, chemical and biological attributes of the environment. They restrain population growth.