Evolution, Biodiversity, and Population Ecology
Biodiversity
the variety of life across all levels of biological organization
Species - a population or group of populations whose members share characteristics
They can breed with one another and produce fertile offspring
Genes
Populations- a group of individuals of a species that live in the same area and freely reproduce with each other
Communities
A diverse system with multiple pathways and redundancies is more stable and less vulnerable to external shock than a uniform system with little diversity
Evolution
Evolution = change over time
Biological evolution = change in populations of organisms over generations
Genetic changes lead to changes in appearance, functioning, or behavior
Directed Genetic Changes:
Natural selection = process in which traits that enhance survival and reproduction are passed on more frequently to future generations than those that do not
Genetics
DNA (Deoxyribonucleic Acid) codes for proteins Each protein is coded for by one gene
Environmental pressures select for increases of traits in populations - example is human skin color
What produces all this variation?
Mutation- accidental changes in DNA that may be passed on to the next generation - This randomly changes traits , Often they are harmful may be selected against
Mutation introduces new genetic variability into population -
Sexual reproduction maintains variability in a population
Speciation - Defined by speciation = the development of so many differences between populations that their individuals can’t reproduce anymore- They are now separate species
Evolution (both micro and macro) is the engine that produces biodiversity
Allopatric speciation (Greek: different country)= species formation due to physical separation of populations-
can be separated by glaciers, rivers, mountains
Each population gets its own set of mutations
Natural selection can speed the process
Sympatric Speciation
Sympatric means ‘Same Country’ in Greek
new species evolve from a single ancestral species while inhabiting the same geographic region
May not be able to reproduce with each other after too many changes -
CHANGE IN BEAKS TO ATTAIN DIFFERNT FOOD SOURCES
Variation - Different traint within population - Beak sizes in Birds
Adaptation - Traits that confer an advantage in particular environment - Longer beaks more likely to survive.
Biotic Potential - an organism capacity to reproduce off springs ( kids)
click to edit
Related species in different environments experience different pressures and evolve different traits
Divergent evolution = speciation, accumulation of differences between two populations over time. DOGS AND WOLVES
Convergent evolution = unrelated species may acquire similar traits because they live in similar environments - EX - BIRDS BATHS AND BUTTERFLY
Evidence of natural selection is all around us
Artificial selection = the process of selection conducted under human direction
Produced the great variety of dog breeds and food crops
We can see the history of diversification by Phylogenetic trees = diagrams that show relationships among species, groups, genes, etc.
Fossil will help to show how old an organism is
Ecology
Ecology and evolution are tightly intertwined
Biosphere = the total of living things on Earth and the areas they inhabit
Community = interacting species that live in the same area
Ecosystem = communities and the nonliving material and forces they interact with
We study ecology at several levels**
Population ecology = investigates the dynamics of population change
The factors affecting the distribution and abundance of members of a population
Why some populations increase and others decrease
Community ecology = focuses on patterns of species diversity and interactions
Ecosystem ecology = studies living and nonliving components of systems to reveal patterns
Nutrient and energy flows
Each organism has habitat needs
Habitat = the environment where an organism lives - It includes living and nonliving elements
Habitat use = each organism thrives in certain habitats, but not in others- Results in nonrandom patterns of use
Habitat selection = the process by which organisms actively select habitats in which to live-
Availability and quality of habitat are crucial to an organism’s well-being
Human developments conflict with this process
Each organism has habitat needs
Habitats vary with the body size and needs of species
Species have different habitat needs at different times- Migratory birds use different habitats during migration, summer, and winter
Species use different criteria to select habitat- Soil, topography, vegetation, other species - Water temperature, salinity, prey -
Water temperature, salinity, prey -
Species survival depends on having
NICHE
Niche = summary of everything an organism does
Use of resources
Functional role in a community: habitat use, food selection, role in energy and nutrient flow, interactions with other individuals
Types
Specialists = species that have narrow niches and specific needs - Extremely good at what they do But vulnerable when conditions change
Generalists = species with broad niches
- Use a wide array of habitats and resources
- Can live in many different places
Population Density
Low densities provide access to plentiful resources and space but make it harder to find mates
Population distribution (dispersion) =
spatial arrangement of organisms
Random = haphazardly located individuals, with no pattern - Trees
Uniform = individuals are evenly spaced Territoriality, competition - Pinguins
Clumped = organisms found close to other members of population - Most common in nature , Clustering around resources , Mutual defense - Fish
Birth Rates and Death Rate 
Survivorship curves = graphs that show that the likelihood of death varies with age
Type I: higher death rate at older ages - Larger animals (e.g., humans)
Type II: same death rate at all ages - Medium-sized animals (e.g., birds)
Type III:** higher death rate at young ages-** Small animals, plants
The influence of some factors depends on population density
The influence of some factors depends on population density
Density-dependent factors = limiting factors whose influence is affected by population density -
Increased density increases the risk of predation, disease, and competition
Results in the logistic growth curve
Larger populations have stronger effects of limiting factors
Density-independent factors = limiting factors whose influence is not affected by population density- Events such as floods, fires, and landslides
Reproductive strategies vary among species
Biotic potential = an organism’s capacity to produce offspring
K-selected species = species with long gestation periods, few offspring, and strong parental care - Have a low biotic potential , Stabilize at or near carrying capacity; good competitors
r-selected species = species that reproduce quickly and offer little or no care for offspring - Have a high biotic potential , Populations fluctuate greatly