Genetics

• What was the atmosphere of early Earth composed of?

  N₂, CO₂, H₂O, CH₄, NH₃
• Why was there very little free oxygen on early Earth?

  Because early photosynthesis did not produce oxygen
• What was the temperature range of early oceans?

  30-55°C
• What was the state of the ozone layer during early Earth?

  There was no ozone layer present
• When did prokaryotic life first evolve?

  Around 3.8 billion years ago
• What are stromatolites?

  Communities of early prokaryotic life
• When did oxygenic photosynthesis evolve?

  Around 2.7 billion years ago
• When did eukaryotic life first evolve?

  Around 2.7 billion years ago
• What event led to the formation of photosynthesizing eukaryotes?

  An endosymbiotic event involving a prokaryote
• What are the three lineages that arose from the primary endosymbiotic event?

  Glaucophytes, Red algae, Green algae
• From which class did Embryophyta evolve?

  Class Charophycea
• What are some common characteristics shared between Charophycea and land plants?

  Cellulose cell walls, starch synthesis, chloroplasts
• What is the reproductive cycle of some Chlorophytes?

  Multicellular haploid gametophyte and diploid sporophyte
• What advantages does a diplobiontic life cycle provide?

  Retention of embryo and production of spores
• What is the term for the alternation of generations in plants?

  Multicellular haploid and diploid stages
• When is evidence of land colonization observed?

  Mid-Ordovician, around 470 million years ago
• What environmental changes occurred during the Cambrian and Ordovician periods?

  Increased terrestrial habitat and soil formation
• What physiological changes occurred during terrestrial invasion?

  Elaboration of sporophyte stage and vascular elements
• When did the evolution of vascular elements occur?

  Around 475 million years ago
• When did the evolution of the cuticle occur?

  Around 450 million years ago
• When did the evolution of stomata occur?

  Around 420 million years ago
• What impact did early land plants have on terrestrial ecosystems?

  Stabilization of river banks and soil formation
• What significant climatic change occurred during the Ordovician period?

  Drop in global CO₂ levels
• What was the climate shift during the mid Devonian and Carboniferous periods?

  From hot and humid to cold and arid
• What happened to CO₂ levels during the mid Devonian and Carboniferous periods?

  Drop by 90% from 3600 to 300 ppm
• What adaptations allowed plants to grow tall during the mid Devonian to Carboniferous?

  Evolution of stele and supporting mechanisms
• What significant evolutionary changes occurred in plant life cycles?

  Transition to heterospory and seed coat development
• When did the Gilboa tree exist?

  385 million years ago
• What were the characteristics of the Gilboa tree?

  Leafless photosynthetic branches, low oxygen soils
• By the early Carboniferous, how many major plant lineages existed?

  Four major plant lineages
• What are the four major plant lineages by the early Carboniferous?

  Sphenopsids, Lycopsids, Filicopsids, Progymnosperms
• When did gymnosperms evolve?

  In the early Carboniferous
• What occurred throughout the Carboniferous to Jurassic periods regarding gymnosperms?

  Rapid evolution and increased geographic distribution
• When did angiosperms first appear in the fossil record?

  Approximately 138 million years ago
• What were the characteristics of early angiosperms?

  Small inconspicuous flowers, often lacked petals
• How did insect pollination benefit early angiosperms?

  Enabled dispersal over long distances
• What are the main evolutionary stages of land plants?

  1. Early Earth conditions
  2. Prokaryote evolution
  3. Eukaryote evolution
  4. Evolution of algae
  5. Chlorophytes
  6. Terrestrial invasion and impacts
  7. Evolution of trees
  8. Early Carboniferous
  9. Evolution of angiosperms
• What were the significant impacts of early land plants on the terrestrial ecosystem?

  Stabilization of river banks and soil formation
• How did the evolution of trees contribute to plant diversity?

  Allowed for taller growth and new habitats
• How did climatic changes influence plant evolution during the Carboniferous period?

  Shifted from humid to arid conditions