Tag Archives: asexual reproduction

Week 8: Unit 4: Continuity and Change

Sky_spectral_karyotype

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Area of Study 1: Heredity

This area of study focuses on molecular genetics and the investigation not only of individual units of inheritance, but also of the genomes of individuals and species. Students investigate inheritance in asexually reproducing organisms and the mechanism and patterns of transmission of heritable traits in sexually reproducing organisms.

Students examine the process of meiosis in terms of inputs and outputs and, in accounting for variations in offspring, consider the interplay between genotype and environmental factors, the significance of mutations in DNA, and the relationship between alleles.

All prokaryotes reproduce asexually, without the formation and fusion of gametes. Many plants and fungi also reproduce asexually, meaning that they are genetically identical to their parent. Types of asexual reproduction include:

  • Binary fission (bacteria)
  • Budding (yeast)
  • Vegetative reproduction (strawberry runners, aloe)
  • Sporulation (fungi, algae, ferns)
  • Fragmentation (annelids, sea-stars)
  • Parthenogenesis (some lizards, sharks and stick-insects)

This week we will begin to study molecular genetics – the foundations of ‘who we are’, before environmental factors play a role. Half your DNA comes from your mother (eggs produced in the ovaries) and half from your father (sperm produced in the testes). This DNA contains genes and genes code for proteins, so the gametes (eggs and sperm) contain the genetic instructions that cross the generation gap, giving you the characteristics that you share with your biological parents.  The genetic instructions in an organism make up it’s genotype, which is expressed visually as the phenotype (physical, biochemical and physiological traits).

Humans have 23 pairs of chromosomes, often referred to as the diploid number or 2n=46. The image above is called a karyotype, used to assist with chromosomal analysis – is this one from a male or female? Chromosomes can be distinguished by their relative size, position of the centromere and the patterns of light an dark bands. Matching pairs are said to be homologous. A human male has non-homologous sex chromosomes (XY).

More Resources for this Unit:

 

Asexual Reproduction

asexual reproduction - hydra

This picture shows asexual reproduction in a hydra by budding. Below is an image showing asexual reproduction in green algae by binary fission. The advantages of asexual reproduction are that it can occur quickly and easily without the difficulty of finding a mate. So in favourable conditions, organisms can reproduce many genetically identical offspring that are well suited to their environment. However, the disadvantages are that there is very little variation in the community, so when environmental conditions change, these organisms may not be able to survive. Sexual reproduction produces much varation, allowing for different environmental conditions.

Video from Britannica.com: Plant reproduction – Asexual Reproduction

Visual Glossary of terms: Asexually Reproducing Organisms

asexual reproduction - algae