Pre-U1: Ecology and Biodiversity - Diversity of Organisms

IBDP BIOLOGY Unit 5 – Ecology and Biodiversity

  • Focus: Diversity of Organisms

  • Authors: T. Albert and T. Honey | Singapore School Cebu

  • Source: Adapted from www.biologyforlife.com and bioknowledgy.info

Variation Between Organisms

Key Concept

  • Variation is a defining feature of life.

Definition of Organism

  • An organism is any biological system that functions as an individual life form.

  • All organisms are composed of cells.

Definition of Population

  • A population is a group of organisms of the same species in the same area.

  • Variation exists among individuals in a population.

Definition of Community

  • A community is made of populations of two or more different species occupying the same geographical area simultaneously.

  • There is significant variation between different species within a community.

Types of Variation

Description of Variation

  • Variation refers to differences among members of a group, which can be:

    • Discrete Variation: Traits categorized distinctly, often influenced by a few genes (e.g., blood type).

    • Continuous Variation: Traits that vary along a quantitative continuum due to multiple genes and environmental influence (e.g., height).

Example of Discrete Variation

  • Examples include:

    • Hand dominance (left or right)

    • Snapdragon petal color

    • Blood type (A, B, AB, O)

Example of Continuous Variation

  • Examples include:

    • Height (e.g., range from 1.5m to 2m)

    • Body mass (e.g., typical range)

    • Traits such as milk yield in cows

Levels of Variation

  • Variations occur at multiple biological levels:

    • Molecular (genomes)

    • Cellular (specialized cells)

    • Organismic (e.g., nerve impulse speed)

    • Ecosystem (between biomes)

Historical Context

Darwin’s Observations (1859)

  • Observed significant variation within species: "No one supposes that all individuals of the same species are cast in the very same mould."

Intraspecies Variation

Definition

  • Intraspecies variation refers to genetic variation within a species.

  • Examples include inherited traits such as spot patterns in giraffes.

Genetic Variation Mechanisms

  • Genetic variation can arise from:

    • Mutation: Changes in gene sequences

    • Gene flow: Movement of genes between populations

    • Meiosis: Formation of gametes leading to new allele combinations

    • Sexual reproduction: Random fertilization leading to varied offspring.

Role of Genetic Variation in Natural Selection

  • Variations enable some organisms to survive better in their environments.

  • Natural selection favors individuals with beneficial variations, leading to evolutionary change.

Variation Between Species

Giraffidae Example

  • The Giraffidae family includes giraffes and okapis, sharing a common ancestor.

  • Variation between organisms is reduced as relatedness increases; diversity is highest among different domains.

Definition of Species

Shared Traits

  • A species is defined as a group of organisms that share common characteristics.

  • The term species originated in the late 14th-century Latin, denoting a class of individuals of a particular kind.

Historical Context of Classification

Linnaeus’s Classification System

  • Carl Linnaeus systematized the grouping and naming of organisms, with species as the most exclusive category.

Limitations of Morphological Classification

  • Traditional classification based on morphology has limitations:

    • Genetically diverging populations can appear morphologically similar.

    • Convergent evolution can lead to similar appearances among unrelated organisms.

Binomial Nomenclature

Definition

  • Scientific naming system using two terms:

    • Genus: First term indicating the genus

    • Species: Second term indicating specific species (e.g., Panthera leo).

Rules for Binomial Nomenclature

  • Genus name: Capitalized

  • Species name: Lowercase

  • Both in italics when printed; underline if handwritten.

  • Genus can be abbreviated after first use.

Biological Species Concept

Definition

  • A species is a group capable of interbreeding and producing fertile offspring, reproductively isolated from others.

Challenges and Limitations

  • Difficulty in determining reproductive isolation due to hybridization, asexual reproduction, and geographical variability.

Hybrids

  • Definition: Offspring from the breeding of two different species (e.g., mules from horses and donkeys).

Example of Hybridization

  • Mules cannot reproduce, hence not classified as a species.

Divergence During Speciation

Concept

  • Speciation is the process where populations diverge to form distinct species, often gradually.

  • Populations can diverge due to physical or behavioral changes when they do not interbreed.

Practical Challenges of Speciation Studies

  • Observing reproduction and breeding success can be logistically challenging in many ecosystems, particularly in the wild or with extinct species.

Chromosomes and Species Diversity

Chromosome Number and Characteristics

  • Definition of a chromosome: A double-stranded DNA molecule that contains genes.

  • Species often have a characteristic number of chromosomes, which affects their ability to interbreed.

Karyotyping

Process of Creating a Karyogram

  • A karyogram shows stained chromosomes arranged in homologous pairs.

  • Banding patterns reveal gene locations.

Genome and Genetic Variation

Definition of Genome

  • A genome encompasses all genetic information, including coding and non-coding sequences.

Trends in Genetic Variation

  • SNPs (single nucleotide polymorphisms) represent a primary mechanism for variation in genes among individuals of the same species.

Human Genome Project

Aim of the Project

  • Completed in 2003 with the goal of determining the sequence of 3.2 billion base pairs of the human genome.

Technological Advancements

  • Innovations in DNA sequencing technology have accelerated the process of genome sequencing and reduced costs significantly.

Applications of Whole Genome Sequencing

Current and Future Uses

  1. Researching Evolutionary Relationships

  2. Personalized Medicine: Tailoring healthcare based on individual genetic profiles.

  3. Ancestry Determination: Tracing family lineage and genetic heritage.