Lecture 9 History of Life Flashcards
what are the six features required for an entity to be considered alive?
- Organization: structurally composed of one or more cells
- Metabolism: system of management of energy and materials via chemical reactions
- Response to stimuli: via changes in growth, alternation of chemical reactions or movement
- Homeostasis: maintenance of some internal chemical and or thermal consistency relative to variation outside of the entity
- Adaptation: ability to change over a period of time in response to the environment
- Reproduction: ability to produce new individual organisms
are viruses alive?
- have n.a. that can mutate and respond to selection
- lack metabolism and homeostasis, and cannot reproduce without using the cellular machinery of a host cell
what does the fossil record do?
- provides evidence of how life has changed over time
what is a fossil?
- preserved remnant/evidence of organisms that lived int the past
what are distinct layers in the ground called?
- strata
what are four influences that raise the probability of something becoming fossilized?
- hard rather than soft bodied
- aquatic rather than terrestrial
- inshore marine rather than offshore
- decomposing organisms are absent
what is our understanding of the diversity and distribution of past life?
- biased and incomplete
what are subfossils?
- fossils that have a higher percent of organic matter
what are the 4 types of fossils?
- casts: form when minerals fill the space in sediment where organism decayed after having been buried
- replacement/petrified fossils: have had their tissues replaced by minerals
- trace fossils: record evidence of behaviour (tracks, burrows, feces)
- preserved fossils: original organic material retained (carbon films, amber, tar, peat, frozen)
what is relative dating?
dating which tells us the order of which fossils are created
ex: sedimentary statigraphy
what are index/indicator fossils?
- fossils that help to “read” incomplete or scrambled layers of sediment
what is absolute dating?
- analyzing radioactive isotopes in fossils or rocks
what is a half-life?
- the 50% of atoms in a given amount of radioactive substance have decayed
what provided the first evidence for continental drift?
- fossil
what are two important mass extinctions?
- end permian: 60% of all families, 90% of marine animal species
- end-cretacious: 20% and dinosaurs
what is adaptive radiation?
- evolution of diversely adapted species from a common ancestor
what are the four chemical and physical processes on early Earth that may have produced very simple cells through a sequence of stages?
- Chemical evolution - abiotic synthesis of small organic molecules
- Abiotic synthesis of macromolecules - joining of these small molecules into macromolecules; small organic molecules polymerize when they are concentrated on a surface
- Packaging of molecules into protocells
- Origin of self-replicating molecules - RNA, ribosomes
how did protocells occur?
- hollow lipid vesicles spontaneously formed
what are protocells?
- fluid filled vesicles that form faster in the presence of volcanic clay
