Diversity of Organisms

Define variation and its cause

Variation is difference between organism (physical, behavior, biochemistry). Causes of these variation include: genetic and environmental factors.

Genes: Genes determine protein an organism is capable of producing. Mutations occur when alleles are combined in different ways in sexual reproduction. 

Environmental factors: environmental temperatures, nutrient availability, oxygen concentration

Distinguish between variation between and within species as well as continuous and discontinuous variation

Between: Classify organism into different group. 

Within: Different individuals have different combination of alleles 

Discontinuous variation: Distinct categories characteristics. (ex: brown vs black fur) 

Continuous variation: Measured on scale/continuous. (ex: height) 

Define morphological species concept and its advantages/limitations:

Species are groups of organisms with shared physical/structural traits. Can be applied to asexula/sexual organism, no information on gene required, applied to extinct fossilized species, easiest and fastest way to distinguish species. But it is very subjective and different individuals in species may appear very different (female/male) aka sexual dimorphism (species appear different based on sex). 

Define the biological species concept and its limitations:

Species is defined as a group of organism that can interbreed to produce a fertile offspring. 

Limitations:

• Asexual reproduction (organism that reproduce asexually is not classified as a species) 

• Fertile hybrids(different species can cross breed to form a hybrid. Not a new species because it needs to be a frequent event) 

• Extinction (extinct species can’t interbreed) 

Define the ecological species concept

Species is a group of organisms that is adapted to particular niche (particular role in environment). It accommodates asexual/sexual species and role of natural selection for organism to adapt to different environmental conditions. 

Con: Niche are difficult to identify because it involves interaction with biotic and abiotic factors. 

Define the evolutionary species concept:

Species is a single lineage of populations from a common ancestor. 

Explain the binomial system

Genus species. 

Typed: Genus species

Handwritten: Genus species

Abbreviation: G. species 

Difficulties of distinguishing between populations and species:

Population is the smallest unit of evolution. Populations evolve not individuals. Hence, it is difficult to distinguish when species have split up (speciation) or evolved.  Speciation is the process of species diverging from same species gradually over a period of time when species are geographically separated and have to adapt to new environment. Once speciation takes place ≠ interbreeding to produce fertile offspring. Because it is gradual = hard to pinpoint = subjective 

Outline the importance of chromosome number of species:

• Same chromosome number = able to breed together successfully (and vice versa)

• Number of chromosome = found in diploid cell (always even) 

• Number of pairs of chromosomes = haploid chromosome number 

• Humans have 46 and chimpanzees have 48

Outline the structure of chromosomes: 

• Made of strands of DNA 

• Section of chromosome = genes = codes for 1 polypeptide

• Chromosomes with centromere located roughly in middle are metacentric chromosomes 

• Chromosomes with centromere at the end are acrocentric chromosomes 

• Chromosomes of cells occur in homologous pairs. Each pair from male and female parent 

• Genes occur at locus (loci plural). Each gene has different alleles (forms).

• Homozygous chromosomes: Diploid organism with same allele of gene at gene’s locus (same base coding) 

• Heterozygous chromosomes: Same gene but different alleles of homologous pairs. 

• Chromosomes are replicated during interphase. Chromatids (half of chromosome) are attached by centromere until they are separated in nuclear division. After division = chromatids → chromosomes 

List the features of karyotypes and how it is used to relate human evolution:

• Length + banding pattern + centromere position + number + appearance of chromosomes 

• Karyogram is a photograph of the homologous pairs in descending order of size and number of an individual’s chromosomes. They are used by genetic counsellors to detect chromosome abnormalities like Down Syndrome 

• Sex chromosomes are not numbered. XX = female. XY= male. 

• Number 1-22= autosomes (body chromosomes)

Evolution of Humans 

• Humans share recent common ancestor with chimpanzees because of similar chromosomes numbers. Humans = 46, chimpanzees= 48 

• The reason why human and chimpanzee split was because a pair of chromosome disappeared from genome or fused with another pair (possibly with chromosome 12 and 13 in chimpanzee) 

• Chimpanzee chromosomes 12 and 13 match the length + centromere position of human chromosomes 2 

• Human chromosome 2 = non-coding DNA (satellite DNA) = location of centromere in chromosome 13 in chimpanzee 

• Banding of long arms of acrocentric chimpanzee chromosomes 12 and 13 = banding of metacentric human chromosomes 2 

NOT Support evolution: 

• Length of 12 and 13 ≠ perfect match of human 2 

• Location of centromere 13 ≠ human 2 centromere

Explain genomes and single nucleotide polymorphism (SNP):

• Genome= all genetic information in an organism. Every DNA in every cell (coding, non-coding, mitochondrial DNA, chloroplast DNA, plasmids)

• All humans share all coding genes with other humans. Differences = different alleles (mutations)

• Single nucleotide polymorphism: difference between DNA sequence from a single base change. (Ex: Majority of people have G base at specific position but due to SNP some have T base). Most SNP ≠ effect on protein but some may lead to altered protein 

Explain genome size and organism complexity:

• Different species = different genome size ≠ more/less is more complex

• Individuals in same species = different genome size because of mutation/environmental factors 

• Similar species can have different genome sizes

• Plants can have polyploidy = cells can have many sets of chromosomes = bigger genome 

• Complexity = brain function not genome size 

Distinguish between eukaryotic genomes

• Varies in size (depends on mass of DNA in nucleus) = some genes are not present in other organisms (ex: plants have photosynthesis genes while humans don’t)  

• Varies in base sequence (found using online databases) 

• Closely related individuals = more similar genomes 

Explain the uses of genome sequencing

• Genome sequencing=

  • Cost of genome sequencing decreasing due to technology

  • Speed of genome sequencing increasing due to technology  

• Phylogenetics= classify species based on evolutionary origins and relationships. Organisms that are grouped together = shared common ancestry. 

• Sequencing technology useful for extinct species or distinguish similar species 

• More similar sequence = more similar species

• Species that are separated for longer = more mutation in mRNA, DNA, amino acid sequence

• More protein/regions of genome = more accurate estimate of evolutionary relatedness 

• Phylogenic trees = diagram that shows evolutionary relationship between species  

Outline the uses of the Human Genome Project:

• Uses genome sequencing to develop genomic medicine (uses info ab genes to design medical treatments) 

• Locate genes that are responsible for human genic disorders (most of them is due to single gene mutation) 

• Development of drugs that targets specific proteins involved in disease (like enzyme inhibitor) 

• Genetic screeing = individuals with high change of developing specific disease are identified for proper treatment (diet, life choices, etc.) 

Explain the difficulties of applying the biological species concept

• Biological species concept: species must produce fertile offspring

  • Compatible mating rituals/sex organs/gametes that fuse tougher/same haploid chromosome number 

• Asexual reproduction methods challenge this as it does not reproduce with a fertile offspring

  • Parthenogenesis: new individual formed without male gamete (virgin birth). All female and clones of mother

  • Binary fission: bacterial cells clones 

  • Vegetative propagation: bulb splits into several new bulbs (clones) 

• Horizontal gene transfer: Passing genetic info from one cell to another in same generation (vertical = next generation). Genes can be transferred within species and between different species ≠ biological species concept (ex: viruses to bacteria/eukaryotes) 

Outline the process of cross-breeding

1. Each parent produces haploid gametes through meiosis (2n → n) 

2. Haploid gametes from each parent fuse to form diploid zygote with full set of chromosomes (2n). Requires both gametes to have same chromosome number

3. Zygote divides to grow into a hybrid organism. Different species with different chromosome numbers = different haploid numbers = failure of gamete fusion/zygote with too many/few chromosomes = infertile hybrid offspring

   1. Mules (Horse and Donkey) is infertile because it has 63 chromosomes. 

Explain dichotomous key and how it works

• A way to identify species using yes/no questions based on characteristics that are clearly identifiable (physical) 

• Each yes/no answer leads to specific species

Define environmental DNA (eDNA) and its relation to DNA barcodes

• eDNA = identify species quickly by extracting DNA from habitat (eDNA sampling)

• DNA barcode= DNA sequence that quickly identifies a species (short sequences. Take from mitochondrial DNA in eukaryotes most of the time or ribosomal RNA in prokaryotes) 

• eDNA sampling process:

  • Multiple eDNA samples taken from habitat 

  • DNA in samples is amplified using PCR

  • Amplified DNA is sequenced (determines base pairs) 

  • Specific sequence within DNA that forms barcode is compared to database of known sequences 

  • Strong match = species identified. Less strong match = more sampling needed