Midterm 2 Flashcards
(72 cards)
What is the Geologic Time Scale (GTS) and how is it structured?
The GTS organizes significant events in Earths history into hierarchal units: eons, eras, periods, epochs, and ages. It allows scientists to study Earths history at varying levels of detail
what is unique about the Hadeon Eon?
the hadeon eon, the earliest eon (~4.6-4.0 bya), contains no fossils and was characterized by extreme conditions like volcanic activity and cosmic bombardements.
what characterizes the paleozoic era?
the paleozoic era (~5401-252 mya) began with the cambrian explosion, marked by the diversification of visible life, and ended with the permian mass extinction.
what is the fossil record, and why is it incomplete?
the fossil record provides evidence of evolutionary history but is incomplete because fossilization requires specific conditions (e.g., burial in sediment) and primarily preserves hard parts of organisms.
what is the difference between relative dating and absolute dating of fossils?
relative dating orders fossils based on their position in rock layers (stratigraphy), while absolute dating uses radioactive isotope decay rates to determine a fossils exact age.
what caused the permian mass extinction?
the permian mass extinction (~252 mya) was likely caused by massive volcanic eruptions in Siberia, leading to global warming and ocean acidification, wiping out ~90% of marine and ~70 of terrestrial species.
what caused the Cretaceous mass extinction?
the Cretaceous mass extinction (~66 mya) was primarily caused by an asteroid impact in Chicxulub, Mexico, leading to the extinction of non-avian dinosaurs and ~50% of marine species.
what is adaptive radiation, and what triggers it?
adaptive radiation is the rapid evolution of diverse species from a common ancestor, often triggered by mass extinctions, novel traits, or colonization of new environments (e.g., mammals after dinosaur extinction).
what did the Miller-Urey experiment deomstrate?
The Miller-Urey experiment demonstrated that organic molecules (e.g., amino acids) could form inorganic precursors under conditions simulating early earth.
What was the Great Oxygenation Event? (GOE)
the GOE (~2.7 bya) was a significant increase in atmospheric oxygen due to photosynthetic cyanobacteria, leading to the extinction of many anaerobic prokaryotes.
what are the key difference between prokaryotes and eukaryotes?
Prokaryotes lack a nucleus and membrane-bound organelles, while Eukaryotes have both. Prokaryotes include bacteria and archaea, while Eukaryotes include protists, plants, fungi, and animals.
How do Prokaryotes reproduce, and how do they achieve genetic diversity?
Prokaryotes reproduce asexually through binary fission. Genetic diversity arises from mutations and genetic recombination via transformation, transduction, and conjugation.
where are archaea commonly found, and what are extremophiles?
archaea often inhabit extreme environments (e.g., hot springs, acidic lakes). Extremophiles are archaea that thrive in extreme conditions like high salinity, low pH, or high temperatures.
what is the endosymbiotic theory, and what evidence supports it?
the endosymbiotic theory posits that mitochondria and chloroplast evolved from engulfed prokaryotic cells. Evidence includes their own DNA, binary fission, and structural similarities to bacteria.
what are protists, and how are they classified?
protists are mostly unicellular eukaryotes that don’t fit into plant, animal, or fungi kingdoms. They are classified into four supergroups: Excavata, SAR, Archaeplastida, and Unikonta.
what key adaptations allowed plants to colonize land?
key adaptations include sporopollenin (protects spores), cuticle (prevents water loss), stomata (regulates gas exchange), and vascular tissue (transports water and nutrients).
what is alernation of generations in plants?
alternation of generations is a life cycle with both haploid (gametophyte) and diploid (sporophyte) stages. in nonvascular plants, the gametophyte is dominant; in vascular plants, the sporophyte is dominant.
what are brophytes, and what are their characteristics?
brophytes (e.g., mosses, liverworts) are nonvascular plants lacking true vascular tissue. They have a dominant gametophyte generation and require water for fertilization.
what are seedless vascular plants, and how do they reproduce?
seedless vascular plants (e.g., ferns, horsetails) have vascular tissue but reproduce via spores. They require water for fertilization due to flagellated sperm.
what distinguishes gymnosperms from angiosperms?
gymnosperms have “naked seeds” not enclosed in fruit, while angiosperms are flowering plants with seeds enclosed in fruits.
what are the structural features of fungi?
fungi have hyphae that from a mycelium, chitinous cell walls, and reproduce via spores. They are absorptive heterotrophs, secreting enzymes to break down organic matter.
how do fungi reproduce sexually and asexually?
fungi reproduce asexually via fragmentation, budding, or spores, and sexually through hyphal fusion, plasmogamy, karygamy, and meiosis.
what is the RNA world hypothesis?
the RNA world hypothesis suggests that RNA was the first self-replicating molecule, capable of both storing genetic information and catalyzing reactions.
what are the causes and effects of mass extinctions?
mass extinctions are caused by events like climate change, volcanic activity, and asteroid impacts. Effects include biodiversity loss, ecological changes, and adaptive radiation of surviving species.
