Evolution Stage 2 Biology Flashcards
(26 cards)
Population
a group of the same species that interbreed in a particular community. One species can consist of several populations which are isolated from one another.
Gene pool
total set of genes that are found in an interbreeding population. All members of the species contribute to the genetic makeup of the gene pool.
Gene pools of different species…
remain isolated as the members of different species do not interbreed and have fertile offspring.
Asexual Reproduction
organisms that produce offspring that don’t involve the production of sperm and eggs undergo asexual reproduction.
- definition of interbreeding don’t apply
Pre-zygotic mechanisms prevent…
reproduction before the zygote is formed.
Temporal (Time) Isolation
Breeding cycles or time of fertility differs from one population of species to the next.
Ecological Isolation
Ecological, habitat or ecological isolation occurs when two species that could interbreed do not because the species live in different areas.
What features do living things share?
Cell membrane composed of lipids
RNA and DNA
Proteins composed of the same amino acids
Water composition by mass is 50%-80% for all cells and water has the same functions in all cells.
The Oldest identifiable evidence of prokaryotes dates back too…
3.5 million
The Oldest identifiable evidence of eukaryotes dates back too…
2.7 million
Cyanobacteria
- formed stromatolites
- are photosynthetic
- important for evolution on earth as they released oxygen into atmosphere.
What processes were thought to be necessary for life to begin?
Synthesis of:
- simple organic molecules e.g. amino acids and synthesis of
- larger organic polymers e.g. proteins
The origin of molecules that can self replicate. I.e. RNA and DNA.
Packaging of these molecules into membranes with an internal environment different in composition from their surroundings.
These structures are known to form spontaneously.
RNA World Hypothesis
proposes that a world filled with RNA-based life predates current DNA-based lifeforms.
RNA World Hypothesis - RNA can self-replicate
RNA is able to store information in a sequence composed of four recurring nucleotides (similar to DNA)
Short sequences of RNA are able to be accurately duplicated to form identical RNA molecules.
RNA World Hypothesis - RNA can act as a catalyst
Modern cells use RNA catalysts (called ribozymes) to remove introns from mRNA and help synthesise new RNA molecules
In ribosomes, rRNA functions as the catalytic component and plays a pivotal role in peptide bond formation
It is believed that prokaryotes evolved before…
eukaryotes
Evidence support eukaryotes evolved second: Fossils
Fossils: earliest eukaryote fossil found, a multicellular alga – 2.1 billion years old
Evidence support eukaryotes evolved second: Biomarkers
Biomarkers – eukaryotic biomarkers have been found in sedimentary rocks in the Earth’s crust indicating 2.7 billion years ago. (Sterols – a molecule only found in eukaryotic membranes)
Evidence support eukaryotes evolved second: Comparison of structure
DNA in eukaryotes has a higher level of organization
Eukaryotes have membrane bound organelles
Eukaryotic cells are bigger
The oldest and most primitive eukaryotes are called…
Protists.
It is believed that eukaryotic cells probably originated as a collection of…
prokaryotes.
The formation of eukaryotes: Step 1
The first step involved folding of the membrane to form the endo-membrane system. This step is thought to have formed the endoplasmic reticulum and most other organelles.
The formation of eukaryotes: Step 2
The second step was the process of endosymbiosis. Chloroplasts and mitochondria seemed to have evolved from prokaryotes which became incorporated after being engulfed by another cell.
Evidence supporting the formation of eukaryotes process.
mitochondria and chloroplasts have inner membranes similar to plasma membranes of prokaryotes, they replicate by splitting through binary fission, they have their own circular DNA and have their own protein manufacturing system including ribosomes.
