When a population has a higher genetic diversity, it’s more likely to survive a natural disaster or a shift in environment
The more traits a population has, the more likely it is that at least some individuals in a population will have the traits needed to adapt to new circumstances
Habitat Diversity
A higher habitat diversity means that more species will be able to thrive
Some organisms require large spanses of land in order to gather enough prey/resources to survive
Specialist species, or species that require a very specific set of environmental conditions in order to thrive, are threatened when habitats are reduced/eliminated
When a population’s size is reduced, leading to a potential loss or change in genetic variation
For example, if a natural disaster (such as a fire) were to randomly eliminate half of a population, then the remaining half might not possess the same genetic diversity as the original population
Founder effect
When a few members of a population leave and start a new colony
The genetic diversity in this new colony will probably have less genetic diversity than the original population
The measurement of a community’s species richness AND species evenness
Species richness
The number of species in a community/ecosystem
Species evenness
How evenly distributed the species are in a community/ecosystem
If species richness is high while species evenness is low, then although there might be a high number of species present, those species won’t be populated/distributed evenly
In the image above, Communities 1 and 2 have the same species richness, but Community 1 has a much higher species evenness; therefore, Community 1 has a higher species diversity
2.2 Ecosystem Services
Ecosystem service
A service or benefit provided to human beings by natural ecosystems
Ecosystem services are classified into four categories
Some services can overlap/fit into multiple categories
Provisioning services
Products that humans receive from ecosystems
Examples: firewood, freshwater, food
Regulating services
Services that naturally regulate the environment
Examples: climate, pollination, flood/erosion control
Cultural services
Non-material services that humans receive from the environment
Examples: tourism/recreation, spiritual connection, mental health
Supporting services
The “core/base” services that allow the environment to maintain/continue its other services
When a colonizing species arrives at a new location, that species will potentially adapt to the very specific set of resources (food/territory) available on the island
Since the species’ adaptations/traits are so niche, the species is considered a “specialist” species (as opposed to a “generalist” species, which is adapted to survive in a range of conditions)
Invasive species
When a non-native species arrives at an island/habitat and outcompetes the native species, it is considered “invasive” and can threaten the balance of the ecosystem
Invasive species are often generalists because they are able to immediately respond to many varieties of resources (food/territory)
Refers to the number of species that an island can support
This “point” is determined by when the rate of new species immigrating to the island equals the rate of species becoming extinct from the island
When an island is closer from a mainland “source” of immigration, the island will have a greater number of species
Having a closer proximity to a biologically diverse mainland means that organisms have to travel less in order to reach the island
Therefore, more organisms will be able to make the journey and immigrate to the island
Conversely, if an island is too far away from the mainland, then very few species will make the trip all the way to the island
Therefore, immigration will be less frequent
When an island is larger in size, the island will have a greater number of species
Many species/organisms require a certain amount of territory for gathering resources
When more land is available, more species are able to access enough land/resources to thrive
Habitat fragmentation
When a large area of land is broken up into smaller patches of land, organisms are forced into limited habitat ranges, and the fragmentation also hinders population diversity (since organisms are reproducing in smaller pools)
Habitat corridors
As a way to avoid human-made habitat fragmentation, environmental engineers have constructed “bridges” or “corridors” of greenery in between habitat patches
This allows organisms to cross over, therefore giving them a wider range of usable territory and the ability to reproduce with a more genetically diverse population
2.4 Ecological Tolerance
Ecological tolerance
The range of abiotic conditions that an organism can withstand
Climate fluctuation can also disrupt ecosystems because changes in temperature and weather patterns might force organisms to adapt to the changes or die off
Although human interference has had an effect on global climate, the earth’s climate also naturally fluctuates over the course of time
Migration
If an environment changes too much, then the species that once populated it might migrate to a new area in search of more favorable conditions
2.6 Adaptations
Genetic diversity
The more genetically diverse a species is, the more likely it is to survive
Varying traits can appear in a population due to both reproduction in a varied gene pool as well as DNA mutations
If a species possesses a variety of traits, and an environmental change occurs that leaves the species with little to no time to react, then it’s possible that at least some of the organisms within the species will have the traits necessary to survive under the new conditions
Organisms with more favorable traits will survive at a higher rate than those with unfavorable traits
Since the organisms with favorable adaptations are more likely to survive, they will reproduce and pass their advantageous traits onto the next generation
Over time, favorable traits will become more common in a population since organisms that lack these traits will die off before having the chance to reproduce
2.7 Ecological Succession
Ecological succession
The process by which a community’s ecological structure changes and evolves over time
Ecological succession might happen following a natural disaster
Ecological succession can be categorized as either primary succession or secondary succession
