radiations and extinctions Flashcards
(123 cards)
1
Q
taxa
A
- heirarchial divisions of species from Kingdoms to subspecies
- group of organisms at any heirarchial rank
- e.g. family or genus
2
Q
are smort or long-lived taxa more abundant?
A
short lived taxa are more abundant
3
Q
what is the average age of species?
A
1-4 million years
4
Q
what are background extinction rates?
A
number of species that would go extinct over a period of time based on non-anthropogenic (non-human) factors
- currently extinction rates are accelerating
- account for 95% of all extinctions
5
Q
why do most organism go extinct?
A
- biological, climatic or physical changes to the environment
- multigenerational loss of reproductive fittness
- habitat attenuation and dissolution
- interbreeding (e.g. neanderthals interbreeding with homo sapiens caused their extinction)
- inability to compete with and displace the resident population
6
Q
what is reproductive fitness?
A
how many offspring can be produced and their ability to reproduce
7
Q
mass extinctions
A
- 5% of all extinctions
- when species vanish faster than they are replaced
- do not tend to be caused by cataclysmic events (e.g. earthquake)
- stochastic = population cannot recover once zero
- rapid = tend to occur within the lifespan of species
- higher survival chances when the geographical distribution is wide
8
Q
what is a radiation?
A
- sudden loss in organism diversity leads to periods of expansion and diverification -> fill in vacant niches
- does not always occur due to an extinction
9
Q
evolutionary radiation
A
- increase in taxonomic diversity caused by elevated rates of speciation
10
Q
what can cause a radiation?
A
- extinction
- major transitions
- ecological specialisation
- major innovations
11
Q
3 steps of ecological theory of adaptive radiation
A
- rapid diverisfication or organisms -> to exploit available ecological niches in the district (mutations accumulate)
- competition between different forms exploiting ecological niches
- specialization results from trade-offs & means that intermediate phenotypes might be selected against
12
Q
what can cause adaptive radiations?
A
- ecological release = population increases when species are freed from limiting environmental factors
- ecological opportunity = environmnetal conditions allow niche availability, new ecosystems emerge
- key innovations / major transition
13
Q
what is adaptive radiation?
A
diversification of a group of organisms where they fill different ecological niches
14
Q
entropy
A
- measure of how energy is distributed in a system
- increased entropy = increased disorder
15
Q
2nd law of thermodynamics
A
- entropy must always increase
- need to “cheat” this to be able to do things such as metabolism
16
Q
local negative entropy
A
- increasing order
- achieved as long as the net entropy of a system is increased
- mini gradual dissipating systems have negative entropy -> osccilate between products and reactants
17
Q
dissipation
A
energy not transferred to useful energy stores
energy wasted / lost to surroundings
18
Q
when did only unicellular life exist?
A
3.8 billion - 900 million years ago
19
Q
when did multicellular life forms emerge?
A
600 million years ago
20
Q
how did multicellular organisms emerge?
A
- from unicellular ancestors
- under well defined environmental conditions
21
Q
key specialisations of multicellular organisms
A
- cell-cell adhesion
- cellular specialisations
- germ-soma seperation
- alterations of life cycle via unicellular intermediates
22
Q
selected synapamoprhies in animals
A
- diploid
- multicellular
- conserved genes for body plans
- posses true epithelia
- develop from a blastula
- eggs develop from 1 of 4 daughter cells in meoisis 2
- aerobic
- non-photosynthetic
- heterotrophic
23
Q
what are synapamorphies?
A
characteristics present in an ancestor and is shared among the evolutionary descendants
24
Q
what are the 2 layers of epithelial tissue found in all animals?
A
- endoderm
- ectoderm
25
endoderm
digestive system and organs like liver, lungs...
develops into gastrodermis (lining of gut cavity)
26
ectoderm
CNS and skin
develops into epidermis (outer layer od body wall)
27
what do the ectoderm and endoderm form?
A developing blastula
28
what is a blastula?
the early stage of an animal embryo
29
mesoderm
- 3rd layer of tissue only found in "higher" animals
- gives rise to muscles and organs between digestive tract and skin, supportive and contractile cells and blood cells
- found in triploblast organisms -> most triploblasts posses organ systems (e.g. digestive system, nervous system...)
30
protostomes
develop mouth first
31
deuterostomes
develop anus first
32
what are HOX genes?
- group of related and very conserved genes in animals
- transcription factors that control the body plan along the head-tail axis
- promote the transcription of certain genes
- vary due to genetic reshuffling
- abundant in different parts of the body e.g define if tail or no tail
33
what is the holobiant concept?
every animal is in a complex community
- bacteria cells outnumber host 10:1
- bacterial genome is larger -> more space for adaptations
34
body plans
group of characteristics shared by a group of phylogenetically related animals at some time
35
adaptive radiation in dogs
- dogs share ancestry with wolves and other canids
- dogs are derived from grey wolves only
- humans "selected" dogs that do well
36
canids
dog-like carnivores
37
not adaptive radiation in dogs example
- reproductive seperation and limited effective population sizes of established breeds
- opportunity for divergence by genetic drift
38
adaptive radiation in dogs example
- breeds under selection for morphological and behavioural traits
- selection due to humans
- breeds that do well are favoured
39
what forms the spectrum of carnial variation?
the combindation of adaptive and not adaptive radiation
- determines things like the bite force or breathing
40
modularity
- independence among groups of phenotypic traits
- if one changes, others are affected
- can help an organism avoid tradeoffs and likely alter the rate & direction of evolution
- may predispose dogs for rapid jaw length evolution
41
dog skull variation
- dogs have more diverse jaws and skulls than wolves do
- jaw comprises a module seperate from the cranium -> changes in jaw can be done without affecting the cranium
- jaw shape can change quite rapidly -> modularity -> due to very few genetic changes (which wont affect the whole skull)
42
dolichocephalic
long-faced breeds
43
brachycephalic
short-faced breeds
44
genetic basis for dog skull variation
- GWAS = at least 5 genetic regions / loci responsible for the cranioskeletal differences between dolichocephalic and brachycephalic breeds
- BMP3 mutation fixed among extreme brachycephalic breeds (pugs)
45
BMP (bone morphogenetic protein)
role in craniofacial development
46
central dogma of molecular biology
replication -> DNA -> transcription -> RNA -> translation -> proteins
47
morpholinos
molecules used & designed to block the activity of certain genes
48
what are species?
- DARWIN=set of individuals closely related resembling each other
- group of organisms with individuals capable of exchanging genes / interbreeding
- a principle taxonomic unit
- when at a certain point genes will no longer flow between two groups
49
what does it mean if an offspring is born highly altrical?
it is underdeveloped
will develop in the marsupium
50
what is the marsupium?
a pouch that protects eggs, offspring and reproductive structures
in female marsupial mammals
51
what are eutherians?
placental mammals
52
how were mammals traditionally classified?
based on the number of openings in the skull
53
anapsida (skull)
no temporal openings
54
synapsida (skull)
one temporal opening
55
diapsida (skull)
two temporal openings
56
what did mammals evolve from?
synapsids
57
which period did true mammals evolve from?
the triassic period (252-201mya)
58
what are ghost linages?
time periods where there is no actual fossil record and other fossils or genetic data is needed
59
mammary glands
- derived from apocrine-like glands
- initial function immune system related?
- need for suckling
60
suckling
ability to draw milk into the mouth from the nipple or teat of a mammary gland
61
hyoid bones
- solitary U-shaped bone in the middle of the neck
- vertebrae throat muscles attached
- muscles needed for the suckling movement
62
why can humans hear more frequencies?
- the "lost" bone wandered to the ear and aids the ability to hear more frequencies
63
what are examples of the only egg laying mammals?
- platypus
- the four echidna
64
distinguishing characters of egg laying mammals
- no teeth
- jaw bones and muscles different
- have two shoulder girdle bones
- hind leg spurs
- use electroreception to find prey
- low metabolic rate
65
placental mammals
- wait longer before they give birth to offspring
- have a more developed placenta
- longer gestation
- shorter time dependent on mother
66
tectonics and mammals
seperation of main mammal clades likely due to pangea breaking up / tectonics
67
what is the main factor that determines if a species will survive a mass extinction event?
geographic dispersal
-> wider geographic dispersal = more chance of finding food and shelter...
68
hamilton´s rule of kin selection
rB > C
where:
r=relatedness
B=benefit to recipient
C=cost to altruist
69
what is a transitional mutation?
- point mutation
- neutral change
- purine to purine
example: T->Cor A->G
70
how many cervical vertebrae to cetaceans have?
7
71
which group of vertebrates have the most variation in estimates of background extinction rate?
amphibians
72
allopatric speciation
species seperate due to a physical barrier like a mountain range or body of water
are now unable to breed with each other
73
sympatric speciation
no physical barrier an members of a population are close together
species seperate due to food barrier or spontanous characteristic developments
74
what is meant by a living fossil?
an extant species with a highly conserved and ancient body plan
75
what are extant species?
species that exist and are not extinct
76
what does speed of speciation depend on?
- time
- geography
- lineage effects
77
what is prezygotic isolation?
- occurs before the formation of a zygote took place
- mating does not need to occur
- occurs faster
- arises earlier among sympatric taxa than alloptric taxa
78
what is postzygotic isolation?
- isolation after members of two different species have mated and produced a zygote
- offspring = hybrid
-> hybrid often unable to mate itself so hybrid production not always considered succesful mating
79
what is reinforcement in terms of isolation?
the enhancement of prezygotic isolation in sympatry by natural selection
80
adaptive trait
enhances fittness (compared to some alternative trait)
81
adaptation / adaptive evolution
changes in living organisms that allow them to successfully live in an environment
82
why do living organisms change?
to cope with biotic/abiotic stresses and pressures
83
what are radiations?
high rates of speciation into diverse groups
84
what are adaptive radiations?
the evolution of ecological and phenotypic diveristy within rapidly multiplying lineages
85
what are adaptive radiations the result of?
divergent natural selection from environments, resources, competition
86
ecological speciation
reproductive isolation associated with different ecologies, often overcoming gene flow
87
what can phenotypic differenatiation between populations or species be caused by?
differences in their environments and resources
88
what does divergence in phenotype result from?
resource competition
89
criteria of adaptive radiations
1. common ancestry
2. phenotype-environment correlation
3. trait utility
4. rapid speciation
90
what is an amniote?
- group of vertebrates that undergo embryonic or fetal development within an amnion.
- include mammals, reptiles and birds
- have a membrane surrounding the fetus
91
where do amniotes lay their eggs?
on land instead of water
92
what is an anamnoite?
- a vertebrate animal that lacks an anmnion, chorion and allantois during embryonic development
- fish and amphibians
93
where to anamniotes typically lay their eggs?
in water
94
caecilians
- amphibians ("blind snakes")
- poor fossil record
- legless, dermal scales, blunt head (digging), retractable sensory tentacles, internal fertilisation...
- 160 species
- found worldwide in tropics except for madagascar and papa-new guinea
95
caudata
- salamanders and newts
- reduced skulls, well developed tails (cant fully fall off), external fertilisation, some lungless (breathe through skin)
- long lived
- 400+ species
- found in the northern hemisphere
96
anura
- frogs and toads
- short, no tail, long muscular hind limbs (for strength and grip), shortened vertebral column (support when jumping), mostly external fertilisation
- 6775+ species
- everyhwere except polar, high altitude and deserts
97
why are there so many frogs?
- anuran radiation after the neobatrachian radiation which accounted for 88% of the frogs
- late crataceous extinction
98
what is a key innovation?
- an adaptive breakthrough or key adaptation
- a new penotypic trait allowing further radiation and success of a taxonomic group
99
examples of key innovations in frogs
- new reproductive modes
-> brook breeding: clustered clutches
- defensive toxins
-> anti-predator defence
- direct development
-> eggs not laid in water and movement towards terrestrial
100
where did birds come from?
- characteristics of reptiles
- some birds used to run on hind legs
- dinosaurs / jurassic birds
101
evidence for evolution of birds
- fossil record
- comparative anatomy
- modern evidence
102
archaeopteryx
- able to fly/glide
- body-axis elongated
- lizard-like
- long tail with feathers in parallel rows
- forelimb: 3 clawed digits
- used as a wing: feathers on ulna and back of hand
- small wing area, rounded shape
- skull like a reptile
- sharp teeth
- enlarged feathers acted as "nets"
103
pygostyle
- in birds
- fused final few vertebrae
- has an evolutionary advantage
- flight control -> allows the bird to manipulate the tail
104
deinonychus antirrhopus
- dromaeosaurid therpod dinosaur
- 3.4m long
- small body, sleek horizontal posture, enlarged raptor claws -> active and agile predator
105
are reptiles cold or warm blooded?
cold blooded
-> can move fast but only for a short period of time
106
bambiraptor feinbergi
- velociraptorine dromaaeosaurid
- no feathers on fossil but classed in feathered group
- enlarged cerebellum -> agility and higher intelligence
- large optic lobes, possible overlapping field of visison -> good vision?
- hindlimb proportions good for running
107
sinosuaropteryx
- most primitive organism found with fossil "feathers"
- not closely related to the achaeopteryx
- furry "down" -> 2 branched filaments
- arboreal -> climbed trees (to avoid predators)
108
confuciusornis
- toothless "beak"
- first with no long tail and a fused vertebrae -> pygostyle
- 6 species identified
-> now widely accepted that birds evolved from dinosaurs
109
cursorial
group up (evolution of birds)
110
arboreal
trees down (evolution of birds)
111
new cursorial theories
- broodingb behaviour
- wing assisted incline running
112
what is the cursorial origin?
- flight evolved from dinosaurs found on the ground
- running bipeds lept into air to catch prey
- wings then evolved for stabilising
- evolution of feathers -> non-flight related
113
non-flight selective reasons for the evolution of featehrs
- display and sexual selection
- shield from heat
- trap insects
- water repellent
- shading (to enable hunting to be easier)
114
problems with cursorial theory
biomechanically untenable
- against downward pull of gravity
- weak mechanical approach
- outcome energetically expensive
- origin of feathers not explained
- origin of brain enlargement not explained
- evolution of flight stroke in ancestors of birds not explained
115
what is the arboreal origin?
- feathers: aerodynamic use - arboreal, gliding animal
- asymmetrical vanes: aerodynamic function
- pennaceous feathers evolved first: origin was flight rather than insulation
- evolutionary needs for feather lengthening: use wings for flight
- feathers as airfoils
116
what are pennaceous feathers?
feathers in the wings
117
cursorial origin: brooding
- wings and feathers on wings used to cover eggs or chicks
- wings are often extended or drooped -> shelter and warmth
- oviraptorid dinosuars may have incubated like modern birds -> similarity between dinosaur and avian incubation
- forelimb position of nesting oviraptorid: selective advantage by increasing area of cover around the adult
- flight used folded wing with elongated feathers a secondary adaptation
118
wing assisted incline running
- seen in current living birds
- proposed as a version of cursorial origin of flight
- aerodynamic functions from running quickly up steep slopes
119
why did flight evolve?
- avoid predators
- invade arboreal habitats
- exploit new resources
- modified locomotory andneurosensory control
- search for mates
- migrate rapidly and cheaply
120
requirements for flight
- low weight & higher power
- high surface/weight ratio
- powerful propellant system -> effective way to move themselves (high temp, high metabolic rate, high performance respiratory and muscular sytsem
121
adaptations for flight
- thin sheets and tubes of bone
- air sacs
- no teeth or heavy jaws
- food eaten quickly digested and have a high energy value
- little accumulation of fat
- young develop outside body (females do not carry young)
122
what is insect sociality?
- living in large groups (supporting / benefiting each other)
123
why live in a group?
