Evolution Flashcards
Parapatric speciation
Occurs when a smaller population is isolated
Sympatric Speciation
When a species evolves from a single ancestry whilst inhabiting the same geographical region
Allopatric speciation
when a biological population becomes separated and isolated from each other, causing them to evolve separately into different species
Molecular clock hypothesis
DNA and protein sequences evolve at a rate that is relatively constant over time + among different organisms
Genetic drift
random changes in allele frequencies caused by sampling error
Convergent evolution
Distantly related species show similar adaptations due to similar selection pressures
Succulent
fleshy stems store water, small leaves reduce water loss, spines deter herbivores
Cacti vs euphorbs
Convergent adaptations to life in arid conditions - separated due human intervention
THe molcular clock
Pairs of species compared for same protein - coding differences highly correlated with divergence derived from fossil data. Genetic differences appear at constant rate
neutral theory
genetic changes arent due to natural selection, but evolve randomly, are neutral
synonymous mutation
change in codon doesnt result in chnage to resulting amino acid
Microevolution
Changes in gene pool of an organism over time
Gene pool
all alleles of all genes of all individuals in a population, representing total genetic variation
Macroevolution
large-scale evolution that occurs at the level of species and above
What is required for life?
Cool temperatures
Gravity
Water
How do cool temperatures promote life?
Allows molecules to keep shape
How does water promote life?
- Solvent for molecules to interact
- Protection from radiation
Protosomes
Organisms whose mouth forms first
Deuterosomes
Organisms whose mouth forms second
protozoan
first or primitive life
Metazoan
multicellular animals
Diploblastic
containing two tissue layers
Triploblastic
containing three tissue layers
Ectoderm
tissue (germ layer) in the outside - gives rise to skin and nervous system
Mesoderm
middle germ layer - gives rise to notochord, muscle, kidney, blood
endoderm
inside germ layer - gives rise to internal organs
Chordate
Animals with notochords
Notochord
‘chord in back’ first tissue to differentiate in chordates
Urochordate
animals with notochords in their tails
cephalochordate
animals with notochords extending into their heads
Echinoderm
prickly skin- groups of animals which include sea urchins
Descriptive biology
experiments aiming to define normal embryonic development, w/ minimal disruption of the process. Lead to understanding what happens during development, but not how, no mechanistic insight into how cells achieve their normal fate
Experimental biology
Experiments which aim to define how embryonic development occurs.
Morphogenesis
Process by which form is generated. Involves coordinated cell movements
Gastrulation
Morphogenetic process by which endoderm, mesoderm and ectoderm layers reach final positions in embryos
Neurulation
Morphogenetic process by which NS begins to forms, especially formation of the neural tube
Blastomere
cell in early embryo
Fate map
Assessment of fate of cell or group of cells based on lineage labelling. Part of descriptive embryology, doesnt require disturbing development.
specification map
Assessment of what a cell or groups of cells will form if removed from embryonic environment. Experimental embryology
Determined
Cell/tissue is determined if it will still develop according to its fate. even when transplanted elsewhere in embryo.
Organizer
Dorsal mesoderm at gastrula stage, which induces overlying ectoderm to become neural and induces neighbouring mesoderm to become somitic
Nieuwkoop centre
region of early dorsal vegetal pole in blastula stage whihc induces the organiser
Arabidopsis
Thale cress
Dictyostelium
Slime mould
Hydra
Cnidarian
Planarians
Flatworms
Caenorhabditis
Nematode worm
Drosophila
Fruit fly
Parhyale
Amphipod crustacean
Strongylocentrotus
Sea urchin
Ciona
tunicate or sea squirt
Brachiostoma
amphioxus
Danio
zebrafish
Xenopus
clawed frog
gallus
chick
Mus
mouse
Advantages of parhyale hawaiensis
- short generation time
- genetics
- sequenced genome
- high regenerative capacity
- transgenesis
- transparent - imaging
-zoa
life
blast-
bud (embryonic)
meta-
after
noto-
back
-uro
tail
cephalo
head
echino
spiny/ prickly
Transplantation experiments aim
assess cells and tissues and whether they can alter the fate of their neighbors.
Experimental embryology
Enforced expression or mutation of genes
Wrong place/time/level.
FInd out what happens.
Experimental embryology
Mosaic development
Stage where cell fates are determined, able to become anything
Regenerative development
stage where cell fates have been determined, but are reliant on neighbouring cells for signal
Competence
Rage of cell fates available to cells/tissues , can be achieved depending on conditions.
Example of cells which are competent to give rise to cell types it would not normally be specified or fated to form
Xenopus
Animal cap cells from blastula stage frog embryos - already fated to give rise to ectodermal tissue, are competent to form any cell in the embryo given the right signals
Induction
Process by which a cell or tissue emits signals changing the fate of their neighbouring cells
Example of induction in development
Induction of neural ectoderm by dorsal mesoderm at the gastrula stage (organiser experiment)
Organiser experiment
Induction of neural ectoderm by dorsal mesoderm at gastrula stage
Homeotic mutation
Mutation leading to transformation of one body structure into another, forms correctly but in wrong place
Hox gene
family of clustered genes in genome which encode related transcription factors characterised by homeodomain
Homeodomain
DNA binding domain
Evidence that hox genes give positional identity along anterior - posterior axis
1) expression pattern
2) Comparative embryology
3) Gene knockout experiments
How do gene knockout experiments give evidence that hox genes give positional identity along A-P axis
remove function of genes lose expression patterning. shows cells are involved in assigning AP patterning
Tandem gene duplication
Unequal cross over due to chromosome mis pairing at meiosis - possibly caused by repeated DNA sequences
Can be segmental or whole duplications
Segmental duplication
Giant tandem duplication, affecting whole chunk of chromosome
Whole duplication events of genome
Can occur by:
Allotetraploidy-hybridization
Autotetraploidy
Allotetraploidy
Hybridization between 2 separate species, formed by meiosis
Autotetraploidy
duplication of genome through improper meiosis
Homologous genes
2 genes you can see share a common answer: extends to paralogous and orthologous genes
Paralogous genes
2 genes sharing a common ancestor within a single genome/organism
Example of paralogous genes
Fetal haemoglobin + adult haemoglobin
Orthologous genes
2 genes share common ancestor, across species
Example of orthologous genes
human and frog insulin gene
Gene redundancy
When no phenotype difference is observed when a gene is mutated due to another gene replacing function of mutated gene, essentially masking it.
Paralogous genes in gene redundancy
Can mask effects of mutated gene. May receive novel functions - partial redundancy
Somite
Segmented blocks in our bodies which give rise to vertebrae, body muscles and dermis in our body axis.
Vertebrae
Morphological structure which can be used to assess AP positioning in the body
HOw many rounds of tandem duplication has there been in mammals and vertebrates
2
Potency
Range of cell fates available to cell or group of cells
Founder effect
loss of genetic variation that occurs when a new population forms by a very small number of individuals from a larger population
Overdominance
condition wherein a heterozygote produces a phenotype better adapted than the homozygote
Analogous genes
Structures with same function but different ancestors
Directional selection
Occurs when conditions favour individuals exhibiting on extreme on a phenotypic range, shifting population frequency curve one way or the other
Disruptive seletion
Occurs when conditions favour individuals at both extremes of a phenotypic range over individuals with intermediate phenotype.
Stabilizing selection
acts against both phenotypes and favours intermediate variants
Transitional form
Individuals showing intermediate states between an ancestral form and that of its descendants
Postzygotic isolation
reproductive isolation due to decreased fitness and inability to mate
Inclusive fitness
Individuals genetic success is derived from cooperation and altruistic behaviour
Hamilton’s law
r x B > C
B - benefit in number of offspring equivalents gained by recipient of altruism
C - cost suffered
r - genetic relatedness of altruist to beneficiary - possibility gene is shared
In plants, the stage of sexual life cycle where cells are haploid is
gametophyte
cytosine methylation is associated with
genomic imprinting
Where is the SRY gene expressed
in the indifferent gonads of male embryos
Evolution occurs under which conditions
heritable traits which vary between individuals and which lead to differential fitness
Haplotype
Combination of closely linked SNPs or alleles on single chromosome
john gurdon experiment
nuclei from differentiated cells from adult or tadpole can be reprogrammed
Incomplete dominance
when dominant allele doesnt completely mask the effects of the recessive gene
