ENVIRON 102 Lecture Notes - Lecture 11: Prochlorococcus, Species Richness, Genetic Diversity
4 May 2018
School
Department
Course
Professor
Biodiversity and Conservation
March 5, 2015 Lecture Notes
Conservation Biology: scientific discipline devoted to understanding the factors, forces, and
processes that influence the loss, protection, and restoration of biological diversity within and
among ecosystems
Genetics and Phenotypes
Most traits are determined by more than one gene – each with multiple alleles
Such traits display continuous variation e.g., height rather than discrete classes e.g., blue vs.
brown eyes)
Each gene contributes to overall height; environmental factors are important too
Natural selection acts by favoring more successful genotypes (other processes exist too)
Genetic variation within populations is a reservoir of opportunity for future change (potatoes and
potato famine)
Origins of biodiversity: Selection
Stabilizing selection, directional selection, and disruptive selection
o May have two food sources and not many food sources for the immediate species
Species Diversity
~2 million species have been formally described by science, but many more exist: estimates range
from 3 million to 100 million
Species are not evenly spread among different groups
Insects comprise about half of all species in the world!
Species not yet discovered?
Prochlorococcus: most abundant photosynthetic organism on earth (100,000 per mL)
~20% of oxygen production?
But not discovered until 1986
How many go extinct before they are ever discovered?
Latitudinal distribution of biodiversity
Species richness increases toward the equator in marine, freshwater, and terrestrial systems
E.g., 30-100 bird species in large area of the Arctic vs. 500-700 bird species in small area of the
tropics
Why is there a latitudinal gradient?
Temperate and polar latitudes: variable climate favors fewer species, and species that are
widespread generalists
Tropical latitudes: greater solar energy, heat, and humidity promote more plant growth to support
more organisms
o Stable climate favors specialist species
o Together these encourage greater diversity of species
Structural complexity and history of disturbance are also important
o Major area of research in ecology
Other factors: Island biodiversity
Island biodiversity hypothesis: the diversity of an island depends on the equilibrium between
processes that bring species to the island and rates of local extinction
)sland target size and distance to mainland affect migration
Island size affects population size which affects extinction
Other islands
Collections of species see the world as islands of habitat
)mmigration rates depend on distance between patches and character of the ocean or matrix
within which patches are embedded
(1) Existing value
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Conservation biology: scientific discipline devoted to understanding the factors, forces, and. Genetics and phenotypes processes that influence the loss, protection, and restoration of biological diversity within and among ecosystems. Most traits are determined by more than one gene each with multiple alleles. Such traits display (cid:498)continuous variation(cid:499) (cid:523)e. g. , height(cid:524) rather than discrete classes (cid:523)e. g. , blue vs. Each gene contributes to overall height; environmental factors are important too. Natural selection acts by favoring more successful genotypes (other processes exist too) Genetic variation within populations is a reservoir of opportunity for future change (potatoes and brown eyes) potato famine) Stabilizing selection, directional selection, and disruptive selection: may have two food sources and not many food sources for the immediate species. ~2 million species have been formally described by science, but many more exist: estimates range from 3 million to 100 million. Species are not evenly spread among different groups. Insects comprise about half of all species in the world!
