Topic 5,6:Origin of species,Origin of Life Flashcards
whats the biological species concept
consists of a group of actually or potentially interbreeding individuals (the offspring must be able to produce offspring themselves) that are reproductively isolated from other such groups
what is the issue with the biological species concept
-it only applies to SEXUALLY reproducing species so the issue is what about asexual species
-it suggests that two different species would never mate and produce offspring (so what about a successful hybrid)
-it suggests that species are a set of organisms adapted to a particular set of resources, called niches in the environment (the issue is at extremes of distribution “species” differs)
-some pops are more unique than the rest
bias in the fossil record
-how different must the fossils be in order for them to be considered species, since we cannot use DNA we can only use their morphology
-sometimes the difference in the morphology could be because one is an adult and the other is a child, not that they are 2 different species
reproductive isolation
the inability of a species to breed successfully with related species due to isolating mechanisms
pre-reproductive isolating mechanisms=Prezygotic
which prevents two individuals from forming a zygote
post-reproductive isolating mechanisms=Postzygtic
occurs after a zygote has formed
Hybrid
a hybrid organism is the result of 2 different species mating
What are prezygotic isolating mechanisms
- Ecological isolation-different habitat or microhabitats that decreases the chance of them meeting therefore mating
- Temporal isolation-when the 2 different species reproduce at a different time (different times of day/seasons)
- Behavioural isolation-their mating signals and pheromones
- mechanical isolation-when their reproductive organs don’t fit
- Gamete isolation- when the sperm and egg cannot fuse (maybe due to the sperm’s inability to break the protein barrier of the egg
Prozygotic isolation mechnaisms
able to overcome prezygotic mechnaisms
-zygote death
-the hybrid is infertile -the offspring can’t reproduce
-hybrid inviability -it has a lower fitness (the ability to survive and or reproduce)
speciation
the process by which one population splits into two or more reproductively isolated pops.
Cladogenesis & anagenesis
- cladogenesis: the branching or spitting of a lineage \
- anagenesis: evolutionary change within a lineage resulting in differences between the sister lineages
Allopatric speciation
when a single population is subdivided via geographical barriers
sympatric speciation
a subgroup can form within a continuous habitat. if the individuals in the subgroup stop mating with the individuals of the larger group, overtime they can reproductively isolate
evidence of hybrids
introgression: incorporation of genes from other species into the gene pool
Reinforcement of reproductive barriers
-natural selection reinforces reproductive isolation mechanisms
-when 2 populations come back into contact :
1. if the reproductive isolation is complete then speciation if its incomplete then hybrids
-if the hybrids have lower fitness than either of the parents, then selection would increase the reproductive isolation between the two
-natural selection favours genes that cause individuals to avoid mating with hybrids (which increases reproductive isolation)->speciation
Reinforcment
when hybrid are left fit than wither parental species, this causes selection against hybrids meaning species continue to diverse until hybridization doesn’t occur again
what are the hybrid zones
- REINFORCEMENT-hybrids are less fit meaning they are selected against therefore the species will continue to diverge until hybridization won’t occur
- FUSION: reproductive barrier weakens until the 2 species become one
- STABILITY: fit hybrids continue to be produced and the 2 species are still separate
fossils
preserves remnants/evidence of organisms that lived in the past
-they are associated with sedimentary rocks
the probability of an organism being fossilised depends on:
-hard rather than soft-bodied
-aquatic than terrestrial
-inshore marine than offshore
-decomposing organisms absent
relative dating
-sedimentary stratigraphy
-this cant tell how long ago the fossil was created, you can just tell which fossil came first, seconds, etc.
Absolute dating
radiometric dating
-there are radioactive isotopes in fossils or rocks
-what occurs is a decay of one isotopic form to another at a constant rate
continental drift
-land masses drift around on plates “floating” on the hot mantel
-tectonic boundaries sites of earthquakes and volcanoes
-relative location of land masses has changed over time
what are the consequences of continental drift
-changes to the environment and climate, which offers an opportunity for diversification of life-this is allopatric speciation
-it also caused mass extinction (ex.Antarctica drifted to the poles and froze solid)
first life from were…
stromatolites
-layers of microbes and sediment
-top layer uses photosynthesis
-lower layer uses top layers by product
the 4 steps of life
- abiotic synthesis of organic molecules
- abiotic synthesis OF MACROMOLECULES
- Formation of protocells
- Self-replicating molecules
abiotic synthesis of organic molecules
inorganic atmospheric gases (methane, ammonia, hydrogen, water vapor, carbon dioxide, nitrogen) +energy (deep-sea hydrothermal vents, collisions. lightning)=organic molecules (amino acids, nitrogen bases, sugar, lipids)
abiotic synthesis of macromolecules
amino acids, nitrogen bases, sugars+ hot sand, clay, or rock -> protein, enzyme, nucleic acids
-RNA monomers are produced spontaneously form simple molecules, they are produced by combining nucleotides and amino acids on hot sand, clay, or rock
formation of protocells
-spontaneous formation of hollow lipid vesicles- cell membrane
-its in the shape of a sphere able to export and keep its own products
Able to confine the organic molecules, which increases the chance of a reaction
-it encourages the evolution of cooperative relationships
-these vesicles formed with the help of volcanic clay
first nucleid acids
-the first genetic material we get is RNA
it’s a single strand, fragile and can self replicate
-they form different shapes depending on the environment
-they can catalyze many different reactions
-it was acted on by natural selection
-now what we use is DNA
it’s a double helix, that is more stable
punctuated equilibrium
that evolution occurs in spurts instead of a slow steady path, so instead of a species evolving slowly into another, all the speciation events occur at once
-it fits in with the concept of adaptive radiation
what abiogenisis
the idea that life arose form non-life
