module 3 Flashcards
Define the term selection pressure
external agent which affects an organism’s ability to survive in a given enivronnment
Define the terms ecosystem, community, population
ecosystem: all of the organisms in a rea plus the nonliving parts of their environment
population: group of the same species living in the same are
community: group of different species living in the same area
List a range of biotic factors
competition, predation, pathogens, plants, animals
List a range of abiotic factors
temperature, availability of water, salinity, availability of light, nutrients,
Compare the structural, behavioral and physiological adaptations that have allowed cane toad populations to rise rapidly
structural:
- tough warty skin which serves as a defence against predators
behavioural:
- nocturnal activity patterns to avoid day time predators and to search for food more effectively at night
physiological:
- secrete a certain kind of fluid called bufotoxin which can be fatal to other animals
Describe the selective pressures that cane toads impose on other organisms
- predation pressure
- competition for resources
- toxicity as a defence mechanism
Define the term adaptation
Adaptations are features that improve the chances of survival of an organism in its specific environment
what is biodiversity
Variety of all living species of organisms
types of bio diversity
Ecosystem diversity → variety of ecosystems in a given place
Ecosystem: community of living things and physical environments as well as the interactions between them
Species diversity → variety of different living species in an area
Genetic diversity → variation of genes within a species
- Provides the variation necessary for natural selection to occur → low species diversity means they are more at risk
Species
interbreeding population that produces fertile offspring young (if given a chance they will not interbreed with other populations
Mass extinction events
selection pressures
- Asteroids → decrease
Rapid changes in climate
-Cambrian explosion → increase because more oxygen in the atmosphere
Anthropocene extinction → anthropogenic (environmental change caused or influenced by people, either directly or indirectly)
human induced:
- climate change
- introduction of new species (eg. predators such as foxes),
- population growth
- introduction of diseases
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Modern evolution theory
all organisms descended from a single common ancestor –> charles darwin –> galapagos finches
Galapagos finches
Birds on different islands in the Galapagos had different beak shape
that were suited for the type of food on each island
- Larger beaks → nuts
- Smaller → insects
- All derived from the same common ancestor
- Divergent evolution → several distinct species from a common ancestor → adaptive radiation
- Each new species adapted to fill an ecological niche eg. eating a specific food source
ecological niche
the role an organism plays in an ecosystem
what is a mechanism for evolution
the process of natural selection –> driven by mtation
Speciation
species arose from a single form of life
Darwinian theory of evolution by natural selection:
evolution occurs as a function of ‘survival of the fittest’ (the continued existence of organisms which are best adapted to their environment) but requires that the ‘fittest’ offspring are also able to pass on their genetic information that determines their more suitable traits
what does natural selection state
- Natural variation exists in a population due to sexual reproduction and mutation
- More offspring are produced that can survive in a population → if population remains to be constant the offspring must die
- Struggle for existence → individuals with traits suited better for the environment will survive → have the opportunity to pass on their genes and reproduce
- Over long periods of time the favourable traits of individuals will become prevalent in the population
- As new adaptations accumulate → population will become different → speciation
Process of evolution
variation, selection pressure, death
variation, selection pressure, survival from those with favourable characteristics, reproduction, passing on favourable characteristics to offsprings, dominance, majority of the population has the favourable characteristics
how do camels show adapttaion
- Long, shaggy fur that keeps them warm but which they can shed during hot months
- Wide hooves keep them from sinking in sand
- Energy-rich fat stored in their humps enables them to survive long periods without food.
law of superposition
Within a sequence of layers of sedimentary rock, the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence
- Shows a change from simple organisms in the oldest rocks to complex organisms in the youngest rocks
Fossils
preserved remains of traces of animals, plants and other organisms from the remote past which allows us to trace the evolution of species overtime
process
- Organism dies
- Layers of sediment accumulate on the top of the dead organism
- The hard parts of the organisms become impregnated with minerals
- Uplift and erosion expose the fossil
Conditions required for fossil formation:
Quick burial → prevents decomposition
Minimum disturbance
Possession of hard parts → less likely to decompose and decay (eg. bones and teeth instead of tissue)
Eventual exposure → so the specimen can be found
types of fossils
body and trace
radioisotope datings
Found in rocks and decay into new (daughter) isotopes that are more stable
- Numerical (age) [absolute] → specific number of years
- Determined through the extent of decay of radioactive isotopes
- Counting the number of new (daughter) isotopes → ratio between the number of radioactive parent elements and the amount of stable daughter elements
Suing the known decay rate to calculator the length of time required to produce a specific number of new isotopes
Relative age –> position
Transitional fossils
Fossils which have characteristics of two different groups of organisms
Whales
- small poorly formed hind leg and teeth → consistent with land carnivores
- Vestigial pelvis and pentadactyl pelvis → consistent with land based vertebrates
Archaeopteryx → first real example of a transitional fossil
- Reptiles
- Toothed beak, wing claw, long tail with many vertebrae
- Birds
- Airfoil wing with contour feathers
Biogeography
Study of past and present geographic patterns of species distribution and ecosystems and the processes that result in such patterns
- Modern distribution of plants and animals supports the theory of continental drift
- evidence
- galopogas finches
ratite birds –> cant fly
Mutation
A change in the DNA sequence of an organism
Codon
three-letter genetic sequence found in both DNA and RNA. It codes for a specific amino acid, or start and stop signals, for the protein synthesis process
Comparing amino acid sequences
Allows you to see the level of similarity between two species
- Molecular clocks
constructed to infer when divergence between two species occurred - Measures the number of changes, or mutations, which accumulate in the gene sequences of different species over time
- Amount of evolutionary change to occur
Molecular evidence for evolution includes that all living things share the same biochemical building blocks
Comparative embryology
- Similarities during embryonic growth highlights that these animals have evolved divergently from a common ancestor
- Embryos of different organisms can be compared as further evidence of evolution
Comparative anatomy
Evolutionary development of species came from examining anatomical similarities between organisms
- homologous and analogous
homologous
structures, body features that are similar in two different species because they were inherited from a common ancestor
Vertebrate skeletons –Vertebrate pentadactyl limb
Analogous structures
These similarities in unrelated species
They are not inherited from a common ancestor
- Dolphins have fins and tails. Sharks also have fins and tails
Vestigial structures
no function within the current species –> Often a leftover from ancestral species → no disadvantage → not selected out by natural selection
Snakes → pelvis and limb bone
Whales → pelvis
Fish and salamanders → eyes (they are blind)
Humans → appendix, wisdom teeth, tail vertebrae
Biochemistry
The more closely related organisms are → the more similar their biochemical makeup is → more likely to have evolved from the other
Evidence of a common ancestor is seen from the universality of DNA as genetic material
Similarities:
All organisms use RNA or DNA → organisms evolved from a single species that used RNA or DNA
All eukaryotes have a similar structure to their chromosomes
All photosynthetic organisms use chlorophyll
All eukaryotes use cytochrome C → respiratory enzyme
Most organisms use haemoglobin (protein used to transport oxygen)
Difference in genes is due to evolution selecting for certain traits
Cladograms
show how organisms are classified based on their evolutionary relationships
Modern examples of evolution
-Antibiotic resistance in bacteria
-DDT resistance in mosquitoes
DDT resistance in mosquitoes
Natural selection → in a population there is genetic variation → some mosquitoes are resistant → use of DDT will kill susceptible mosquitoes leaving the resistant ones → they will survive and reproduce →over time population will become resistant to DDT
Antibiotic resistance in bacteria
- In a population of bacteria, variation exists due to mutations → some are resistant to antibiotics while others are not
- Antibiotics are added → acting as selection pressures
- Bacteria with gene for antibiotic resistance will survive, reproduce (via binary fission: asexual reproduction by a separation of the body into two new bodies) and pass on this trait to offspring → trait of resistance is the favourable trait in the environment
- Over time → new resistant strain of bacteria will develop
How is gene resistance passed on
Vertical gene transfer
Bacteria reproduces very quickly → develop mutations in short spans of time → the mutation that survives passes on the mutation → the whole population becomes resistant
Horizontal gene transfer
Passes on to a different species of bacteria → not its offspring
order
prokaryotes
eukaryotes
jawless fish
reptiles
non-vascular plants
terrestrial organisms
dinosaurs
mammals
angiosperms
Causes of evolution:
- Genetic drift:
The change in frequency of an existing gene variant in the population due to random chance
Blue eyes and brown eyes get married but all offspring might have brown eyes → blue eyes are eliminated by chance - Gene flow:
Introduction of genetic material (by interbreeding) from one population of a species to another
Changes the composition of the gene pool → sum of a population’s genetic material at a given time
A bee carrying pollen from one flower population - Bottleneck effect:
The size of a population is severely reduced
Caused from major events such as natural disasters - Founder effect:
When a small group of individuals breaks off from a larger population to establish a colony
Microevolution
Happens on a small time scale → one generation to the next within a population
Change in frequency of a gene population
Four types
- Mutation
- Migration
- genetic drift
- natural selection
Macroevolution
Major evolutionary change, patterns and processes → above the species level → beyond intraspecific
Horse → selection pressure of predators and food
Modern horses run on a single toe → allows them to outrun predators
Fossil records show that ancestors had many toes → pentadactyl limb
Evolved large flat molar → allows them to break down the tough grass that has become abundant
Punctuated equilibrium
- little to no change in organisms as there are little to no new selection pressures
- In times of sudden environmental stability (floods etc.) → change occurs more rapidly amongst populations especially if they are small in size
Gradualism
increases gradually at a very steady, slow rate
Adaptations
features that improve the chances of survival of an organism in its specific environment
- Structural
- Behavioural
- Physiological
structural
anatomical and morphological features that allow a species to survive in the environment where it lives
Behavioural
actions and behaviours of an organism acts to increase its chances of survival
Physiological
modifications of internal functions that assist the organism survival in its environment and its metabolism
Animal adaptations
Structural adaptations
- Fur and feathers → insulate for hot and cold weather
- Feathers and fur can reflect or absorb solar radiation (darker more lighter less)
Behavioural adaptations
- Nocturnal and diurnal → forage in milder conditions and avoid heat loss
- Burrows → keeps away from extreme conditions on the surface
Physiological adaptations
- Changes in metabolism or production of different chemicals (eg. sweat/venom)
- metabolic activity
Hibernation → inactive state resembling deep sleep to help survive cold climates (behavioural as well)
Plant adaptations
Structural adaptations
- Thick waxy cuticle to reflect the suns heat and reduce water loss
- Eucalyptus leaf hang vertically
Behavioural adaptations
- Respond to the environment through their growth and movement
- Detect sunlight
Sun changes direction the plant will change direction (phototropism)
Physiological adaptations
- Close stomata during low humidity high temperatures
Open during the morning, late afternoons, night
Divergent evolution
process where two or more populations of a species become less similar (diverge)
Sympatric speciation
- Ancestral species evolve into two separate species within the same physical or geographical location → slight behavioural modifications
Allopatric speciation
- Ancestral species become physically or geographically separated → they evolve independently which leads to separate species
Earthquake, volcano, climate change
Convergent evolution:
process by which unrelated (or distantly related) organisms evolve to become more similar (eg. body form, colour, behaviour, organs)
- Wings in bats, insects birds
Due to similar selection pressures and ecological niches → wings have independently rise
Coevolution
when two or more species reciprocally affect each other’s evolution through the process of natural selection eg bees and flowers
Cane Toads
- Deliberately introduced from Hawaii to control the population of scarab beetles that are infesting sugarcane crops
- Beetles were on the top of the plant that the cane toads could not reach
Tough and adaptable species → poisonous, few predators
Expanded their range rapidly → slow toads were at the back of the invasion front whereas the fast toads (bigger and longer legs) were at the front
Selection pressure driving the movement of the toads → colonising new areas so they don’t have to compete for food, bodies of water, mates
In order to control the population → physical traps
Toxin to lure the tadpoles
