Module 4_ Biodiveristy and Evolution

Biodiversity

• Biological diversity - variation of life forms on Earth.

Scales of Biodiversity

Ecosystem Diversity

• Refers to the range of different habitats or ecosystems within a region.

• Example: Jamaica Bay, NY includes wetlands, barrier beaches, mudflats, and salt marshes.

• High ecosystem diversity correlates with high species diversity.

Species Diversity

• Species Diversity- The number of different species in a region or habitat

• Species- individuals capable of mating and producing viable offspring.

  • Approximately 2 million species have been identified, with estimates of 5-100 million total on Earth.

    • Notable discoveries include:

      • Pinocchio frog (2010)

      • Sea slug (2014)

      • Olinguito (2013)

      • Sparklemuffin peacock spider (2015)

Species Diversity and Insects

• About 900,000 insect species are known, constituting 80% of described species.

• Estimates suggest 2-30 million species of insects exist, with about 10 quintillion individuals alive at any one time.

Species Richness and Evenness

• Species Richness- Number of different species in an area. A fundamental measure of biodiversity.

• Species Evenness- Measures the relative abundance of different species, indicating how equally individuals are distributed across species.

• More evenness implies greater diversity.

Simpson’s Diversity Index

• Created by Edward H. Simpson in 1949.

• Considers both species richness and evenness.

• Scores range from 0-1

  • Scores near 0 indicate low diversity, while scores near 1 indicate higher diversity.

Genetic Diversity

• Measures genetic variation among individuals within a species.

• Populations with higher genetic diversity tend to have:

  • Increased resilience to disease.

  • Greater reproductive success.

  • Enhanced survival of individuals reaching maturity.

Types of Diversity

• Genetic Diversity: The variety of genetic information present in a population.

• Example: The Mauritian Pink Pigeon had a population of 10 in 1991 due to conservation efforts, reflecting a low genetic diversity.

Evolution as the Mechanism of Biodiversity

Evolution: Change in the genetic composition of a population over time.

Types of Evolution:

• Microevolution- Change within a single population (below the species level).

• Macroevolution- Evolution that results in new species or larger taxonomic groups.

Mechanisms of Evolution

• Evolution occurs primarily through:

  • Artificial selection- humans determine which individuals breed

    • domesticated animals

    • crops

  • Natural selection- the environment determines what individuals are to survive and reproduce naturally

• Random processes- genetics change over time by mutation

  • Mutation- a random change in the genetic code

    • Not all mutations are by evolution

      • Somatic mutation- occurs in non-reproductive cells and won’t be passed on to offspring

    • Mutations that occur in reproductive cells (egg and sperm) can be passed on to the offspring

    

  • Genetic drift―change in the genetic composition of a population over time as a result of random mating “Survival of the luckiest”

    • more detrimental to smaller populations

  

  • Bottleneck effect- a reduction in the genetic diversity of a population caused by a reduction in the number of organisms

    • Habitat loss, natural disasters, hunting, etc

    • drastically decrease in population size

    

  • Founder effect- a change that occurs in a population descended from a small number of colonizing individuals

    • One leaves and brings its genetics with it

Darwin's Theory of Evolution

• Explains the principles of natural selection and adaptation.

• Key points include:

  • Overproduction of offspring.

  • Variation within species.

  • Differential survival and reproduction based on advantageous traits.

Pace of Evolution

The rate at which a species evolves is dependent upon:

• The rate of environmental change

• The amount of genetic variation in the species

• The size of the population involved

• How fast the species reproduce

Population Characteristics

Size- the total number of individuals within a defined area at a given time

Density- the number of individuals per unit area at a given time

Distribution- how individuals are distributed with respect to one another

Sex ratio- the ratio of males to females

Age structure- how many individuals fit into particular age categories

Understanding these factors is crucial for predict population size and create conservation strategies

• ex: white rhino

Factors that Influence Population Size

Density-dependent factors- Cause a population’s growth rate to change (typically decrease) with increasing population density

• limiting resources

  • plants for water and soil nutrients

  • animals for food, water, nesting sites, and disease

Density-independent factors- affect growth rate independent of population density

• natural disasters

Growth Model

Growth models help ecologists understand population change with equations used to predict population size.

Exponential growth model- The future size of the population (Nt ) depends on the current size of the population (N0 ), the intrinsic growth rate (r), and the amount of time (t) the population grows

Logistic growth- when a population whose growth is initially exponential, but slows as the population approaches the carrying capacity

Carrying capacity (K)- the limit of how large a population can be sustained by the limiting resources, especially food

• number of births = number of deaths

• die off/population crash occurs when you go past the carrying capacity

  

Species Interaction

Competition- struggle over limited resources

• Competitive exclusion principle- two species competing for the same limiting resource cannot coexist

Predation- use of one species as a resource by another

• True predators- kill their prey

• Herbivores- consume plants as prey

• Parasites- live on or in the organism they consume

  • If they cause disease, they are pathogens

• Parasitoids- lay eggs inside other organ

Mutualism- benefits two interacting species by increasing both species’ chances of survival or reproduction

• Ex: Aacacia tree and acacia ant

Commensalism- a type of relationship in which one species benefits but the other is neither harmed nor helped

• Ex: barnacles on a whale

  • Barnacles benefit from the whale while the whale gets nothing

Laws vs Theories

Scientific Law- description of an observed phenomenon

• law of gravity

Scientific Theory- explanation of observed phenomenon

• theory of relativity