deck_1141064 Flashcards
Evolution
Changes in the genetic make-up of populations of a species over generations.
Factors that cause evolution.
- Natural selection- Gene flow- Genetic drift- Bottlenecking- Non-random mating
Use and disuse
Belief that the environment modifies traits.E.g., a giraffe’s neck lengthens due to it stretching to reach leaves.
Inheritance of acquired traits
Belief that acquired traits are passed on to offspring.E.g., the aforementioned giraffe passes on this trait to its offspring.
Gene flow
The mixing of genes through immigration and emigration.
Genetic drift
When random changes occur in the genetic make-up of a population. Most significant in small populations.
Bottlenecking
When the original population has genetic diversity, but an event causes similar groups to be wiped out. The remaining population is very homogenous.
Non-random mating
Occurs through:- Inbreeding- Sexual selection
Hierarchy of biological order
- Atoms- Molecules- Organelles- Cells- Tissue- Organ- Organ System- Organism
Atom (e.g.)
Oxygen atom
Molecule (e.g.)
DNA
Organelles (e.g.)
Cell nucleus
Cells (e.g.)
Cardiac muscle cell
Tissue (e.g.)
Cardiac muscle tissue
Organ (e.g.)
Heart
Organ system (e.g.)
Circulatory system
Organism (e.g.)
Zebra
What are the smallest units of life?
Cells
Scientific method
- Observations- Question- Hypothesis- Prediction- Test (experiment or additional observation)If correct, retest. If incorrect, revise or replace hypothesis.
Charles Darwin
Discovered the mechanism for evolution and developed the theory of evolution through natural selection.- Carapace shape in Galapagos tortoises- Marine iguanas adapted to eat algae- The Origin of Species- A. Wallace developed same theory
Darwinian evolution
A gradual change in populations over time as a result of natural selection.
Species survival relies on the abilities to…
- Obtain resources- Survive- Reproduce
Modern synthesis of evolution
- Individuals that make up a population are not identical.2. Some of this variability is heritable, passing in genes.3. In most generations, more offspring are produced than can survive.4. Survival and reproduction are not random effects, but those best able to obtain resources, survive, and reproduce will pass on their genes.
Other causes of evolution
- Gene flow- Genetic drift- Bottlenecking- Non-random mating
Gene flow
The mixing of genes through immigration and emigration.
Genetic drift
Random changes in the genetic make-up of a population over time. These are most significant in small populations. E.g., eye color in people.Types:- Population bottleneck- Founder effect
Founder effect
When a small population of a colony breaks off and the genetic diversity of this smaller colony is much more homogeneous, misrepresenting its founder.
Non-random mating
- Inbreeding- Sexual selection
Microevolution
Evolution that does not result in a new species, but changes the genetic make-up of existing populations. - Most common
Macroevolution
Evolution that results in a new species. - Rare, requires special circumstances and a significant amount of time. - Also called “speciation.”
Artificial selection
Done by humans. E.g., crops and domestic animals.
5 Kingdoms
- Plantae (eukaryotes)- Fungi (eukaryotes)- Animalia (eukaryotes)- Protista (eukaryotes)- Monera (prokaryotes)
Spontaneous generation
Incorrect hypothesis that life originated from non-living things.
Biogenesis
Synthesis of organic compounds from inorganic precursors.
Inorganic compounds
Do not possess a carbon skeleton. May possess one carbon atom.
Louis Pasteur
Conducted experiments to show that life comes from life, supporting his biogenesis hypothesis. - Chicken broth in flasks with straw
The first life form was…
Anaerobic and prokaryotic
Protobiont
Abiotically formed cell.
Hypothetical steps to formation of the first cell
- Assemble simple molecules into building blocks for complex polymers2. Assemble polymers that can store information and catalyze reactions.3. Add membranes and an energy source to make a living organism.
Phospholipids
Form vesicles in water.
Organic compounds found in cells
- Proteins (amino acids)- Sugars- Fats- Genetic material (DNA/RNA)
Ribozyme
RNA molecule that was likely the first molecule to carry genetic information, replicate itself, and speed up chemical reactions.
Steps to abiotically formed cells
- Spontaneous formation of lipids, carbs, amino acids, proteins, and nucleotides.2. Formation of protein-RNA systems and lipid spheres.3. Self-replicating system enclosed in selectively permeable, protective lipid sphere.4. Membrane-bound protobionts5. Living cells (prokaryotic and eukaryotic)
History of life on Earth summarized
- Abiotic synthesis of small, organic molecules.2. Joining of molecules into polymers (chains of organic molecules)3. Origin of self-replicating molecules as genetic material.4. Packing of these molecules into protobionts, formed by many abiotically produced molecules.5. First cells anaerobic and prokaryotic, followed by aerobic and photosynthetic prokaryotic cells.6. Eukaryotic cells are formed, initially single-celled and then multicellular.
Prokaryotic cell structure
- No interior membrane for nucleus- May have flagella for locomotion- Pili for grip- Gelatinous outer capsule - Cell wall - Plasma membrane - Cytoplasm - Nucleoid + Contains genetic material - Plasmid + Carries resistance to antibiotics - Ribosomes
Prokaryote shapes
- Bacilli- Cocci- Spirochetes
Bacilli
Rod shaped
Cocci
Spherical
Spirochetes
Spiral shaped
Prokaryote
Single-celled (usually) organism that has neither a distinct nucleus with a membrane nor other specialized organelles such as mitochondria or chloroplasts.
In what order did prokaryotes and eukaryotes evolve?
- Heterotrophic prokaryotes2. Autotrophic prokaryotes (photosynthesis) a) Do not possess chloroplasts but may possess chlorophyll.3. Aerobic respiration4. Unicellular eukaryotes5. Multicellular eukaryotes
Endosymbiotic theory
Origin of eukaryotic cells: - Ancestral prokatyote’s plasma membrane unfolds to form the endoplasmic reticulum and nucleus.- This cell then engulfed aerobic heterotrophic prokaryote cells which developed into mitochondria. + These cells became heterotrophic eukaryotes. - Animals and fungi today.- Some of the cells also engulfed autotrophic prokaryote cells which developed into plastids, or chloroplasts. + These cells became photosynthetic eukaryotes. - Plants and algae today.
Eukaryotic cell structure
- Contains a nucleus with DNA as well as mitochondria and other organelles. + These organelles are membrane-bound.- Autotrophic eukaryotes will also possess plastids, or chloroplasts.- Contains a plasma membrane, cytoplasm, and other structures found in prokaryotes.