ANIMAL SYSTE

• An animal is defined by four features: 

  • (a) eukaryotic cells, 
  • (b) multicellularity for most of its life cycle, (unicellular during embryonic stage)
  • (c) obtaining much of its food by eating, and 
  • (d) having at least one self-powered mobile stage in its life cycle.
• Red shift. If a galaxy is moving away from us (due to the expansion of the universe), the light coming from it is shifted to the red end of the spectrum of visible light wavelengths. If a galaxy is moving towards us, the light is shifted towards the blue end. All galaxies show a redshift, it means the universe is expanding.
• Life is defined by three key features: 

  • reproduction, 
  • autonomy from the surrounding environment, 
  • and being bounded by membranes with the capacity for self-repair.
• • Stromatolites, composed of prokaryotic fossils, were among the earliest fossils, predating multicellular animals.
• The Ediacaran period followed the Marinoan glaciation and featured the Ediacaran biota, which persisted until the transition to the Cambrian period
• • One hypothesis for the evolution of multicellularity suggests that the ability of cells to stick together enabled this transition. Cadherins, proteins responsible for cell adhesion in animals, were present in ancestral forms before multicellularity evolved.
• Development, the process of making a multicellular adult from a fertilized egg
• Evolutionary change in multicellular organisms occurs through alterations in developmental stages from one generation to the next, known as heterochrony
• • Anomalocaris: Name translates to "odd prawn."
• • Hallucigenia: An unusual animal with unresolved body form interpretations.
• • Pikaia: Not an arthropod; closer to vertebrates due to specific anatomical features.
• Charles Darwin's book “On the Origin of species” introduced the natural selection or survival of the fittest. Individuals whose traits are best suited are more likely to survive and reproduce.
• Primary producers are photosynthetic bacteria, cyanobacteria, and chemosynthetic bacteria.
• Speciation formation of new species

  • Requirements:
  • Divergent changes- population must evolved distinct traits due to differences in environmental condition
  • Reproductive isolation - prevent interbreeding between populations
• Wallace effect, where selection acts against individuals who engage in mating with members of other incipient species, reinforcing reproductive isolation.
• Variation, comes from mutations, genetic recombination, and independent assortment
• Polymorphism refers to the existence of two or more distinctly different forms of a species in the same geographical area
• Fitness, defined as the probability of surviving to adulthood and/or having offspring
• Balancing selection occurs when natural selection maintains multiple alleles or phenotypes in a population instead of favoring one over the other.
• • Apostatic selection results in a balance between different forms of a species. 
• • Species two animals are members of the same species if they can reproduce with each other in nature - usually with the condition that they are of opposite sexes.
• Reproductive isolation - prevent interbreeding between two different specie