Hadean
This is why we aren't sure how life first started.
There are no fossils/evidence.
This major evolutionary step allowed cells to specialize and work together, making it possible for larger and more complex organisms to appear for the first time.
What is multicellularity?
These early land vertebrates evolved from fish and were the first to walk onto land, but they still had to stay near water because their eggs and skin would dry out easily.
What are amphibians?
This event triggered wildfires, blocked sunlight, collapsed food webs, and brought an abrupt end to the non-avian dinosaurs at the close of the era.
What is an asteroid impact?
These living primates are humans’ closest relatives, sharing a recent common ancestor with us and providing key clues about how early hominins might have behaved.
What are chimpanzees?
This term describes the idea that life arose from nonliving chemicals on early Earth.
What is abiogenesis?
These complex cells, which contain a nucleus and specialized internal structures, evolved after oxygen levels rose enough to support higher-energy life.
What are eukaryotic cells?
These early amniotes evolved scaly skin and hard-shelled eggs, allowing them to break free from water and become the first fully terrestrial vertebrates.
What are reptiles?
This catastrophic event at the end of the Paleozoic wiped out most marine and land species, clearing the way for dinosaurs to rise and dominate in the Mesozoic.
What is the great dying?
This key adaptation in early hominins freed the hands for carrying tools and food, improved long-distance walking, and is defined by moving on two legs as the main way of getting around.
What is bipedalism?
Early life forms were simple, single-celled organisms similar to these modern cells that have no nucleus.
What are prokaryotes/bacteria?
According to endosymbiosis, complex cells formed when one cell engulfed another and kept it. Name one organelle that formed this way.
What is a mitochondrion or chloroplast?
This event marks the sudden burst of new animal body plans and major groups, when life rapidly diversified and many familiar forms first appeared in the fossil record.
What is the Cambrian Explosion?
These descendants of reptiles rose to dominance after the Great Dying and became the ruling land animals of the Mesozoic, spreading into many sizes and forms across the planet.
What are dinosaurs?
Some scientists argue that human activity has changed Earth’s climate, landscapes, and ecosystems so dramatically that it marks the start of a new chapter in geologic history, often referred to by this name.
What is the anthropocene?
Once this process evolved, oxygen began accumulating as a waste product, reshaping conditions for life on Earth.
What is photosynthesis?
What effect did the evolution of sexual reproduction 1.2 billion years ago have on life?
It increased genetic diversity and sped up evolution.
These early marine arthropods with hard exoskeletons were among the most common and successful animals of the Paleozoic, leaving behind abundant fossils.
What are trilobites?
These small, mostly nocturnal animals first appeared during the Mesozoic but stayed in the shadows while dinosaurs dominated, surviving by eating a wide range of foods and hiding in safe places.
What are mammals?
This group of mammals—including lemurs, monkeys, apes, and eventually humans—evolved adaptations like grasping hands and forward-facing vision that helped them thrive in tree-filled environments.
What are primates?
These layered, rocky structures formed by ancient microbial mats are some of the oldest visible evidence of life on Earth.
What are stromatolites?
This major atmospheric shift was triggered by early photosynthetic microbes releasing oxygen, transforming Earth’s oceans and air while also wiping out many anaerobic organisms in one of Earth’s earliest mass extinctions.
What is the Great Oxygenation Event?
These animals first appear in the fossil record during the Paleozoic as simple, fish-like forms with a backbone, beginning the long evolutionary line that later led to amphibians, reptiles, birds, and mammals.
What are vertebrates?
After the asteroid impact ended the Mesozoic, only one lineage of dinosaurs made it through the global collapse. This surviving group was small, adaptable, and able to exploit many different food sources, allowing it to eventually spread worldwide.
What are birds?
Name two examples of the large Ice Age animals that disappeared as humans spread across the world, through a mix of climate change and hunting pressure.
Answer:
woolly mammoths, saber-toothed cats, giant ground sloths, Irish elk, mastodons?