Evolution and Biodiversity Flashcards
Species
A group of organisms that can interbreed and give fertile offspring.
Population
A group of individuals of the same species living at the same area at the same time.
Gene Pool
All the possible genes and their alleles within a species.
Speciation
The process where a new species is formed from a pre-existing species.
Evolution
A gradual change in the heritable characteristics of an Individual.
Directional Selection
Selection that favors individuals on one end of the phenotypic distribution.
Individuals not favored die out.
Increase in dark moths during industrial revolution, when the pollution caused darkening of the trees, so the white moths
were more visible to the predators.
Stabilizing Selection
Selection that favours individuals in the middle of the phenotypic spectrum.
Both extremes in the spectrum of a characteristic are not favoured by the environment.
Sickle cell anaemia. Individuals that are homozygous either for healthy cells, or sickle cells will be exterminated in the areas exposed to malaria.
The heterozygous individuals will have both resistance to malaria and a decent oxygen carrying capacity to be favoured by the environment
Disruptive Selection
Eliminates individuals with the intermediate characteristics.
Only both ends of the phenotypic variation will be favored by the environment.
Squirrels with long tails are good at balancing themselves on the trees, squirrels with short tails are faster at running away from predators on the ground.
The squirrels that have intermediate tails are easily caught by the predator on the ground, but also on the trees, as their balance is not as good
Temporal - Reproductive Isolation
Occurs when two populations stop interbreeding because of differences in their mating times.
Maggot fly, which in North America used to leave its eggs on the hawthorn fruits, which were the food for its larvae.
With the introduction of non-native apple trees, it started leaving eggs on those as well.
However, since the two fruits ripe at different times, depending on which fruit the fly leaves its eggs, it will mate at different times.
Therefore within the population, there is a temporal mating barrier.
Behavioural -Reproductive Isolation
Geographical - Reproductive Isolation
Individuals of the same population become
separated geographically and can therefore not mate anymore.
Lava lizards from Galapagos. A group of lizards managed to get from one
island to another
As they couldn’t return anymore, they could only interbreed
with the population that went to the island.
Over time, the interbreeding of
the lizards on one, and on the other island, created two different species of lizards.
Geographical - Reproductive Isolation
Individuals of the same population become
separated geographically and can therefore not mate anymore.
Lava lizards from Galapagos. A group of lizards managed to get from one
island to another
As they couldn’t return anymore, they could only interbreed
with the population that went to the island.
The interbreeding of the lizards on the other island, created two different species of lizards.
Gradual and Abrupt Speciation
There are full fossil records showing the gradual change of species over time.
Environmental pressures and species adaptation would eventually lead to accumulation of new characteristics that differ one older species from a newer one.
There are incomplete fossil records where the lack of intermediate fossils could be explained by a more abrupt evolution.
This could happen through genetic mutation, like doubling of the chromosome numbers that result in organisms that are incompatible with their parental species.
Polyploidy is an example
Polyploidy
Individuals of the same species have the same number of chromosomes.
Non-disjunction of chromosomes during meiosis may result in gametes with double the number of chromosomes.
If such a gamete is fused with a normal, haploid gamete, the offspring
become triploid, and therefore infertile since they cannot divide their chromosomes in half.
Results in a new species since its individuals cannot mate with other members of the species and produce fertile offspring.
Evolution
Accumulation of changes in heritable characteristics of a species over time.
Over time, certain characteristics of a species change, and if these
characteristics are inheritable, then this change is transferred to all the subsequent
generations.
Adaptation
The process of change by which an organism or species becomes better suited to its environment.
If the members of species become separated for a long period of time, due to adaptations in their new environment will start changing as well.
Sometimes it happens that these two populations change so much that, even if they got reunited, they would not be able to interbreed anymore.
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds &
Pentadactyl Limb
Amphibians, reptiles, birds & mammals use their limbs fro running, walking, swimming or jumping
The basic bone structure of this limb is the same in all vertebrates, pentadactyl limb
They probably shared the same ancestor, and due to their different environments the same limb adapted to suit the type of locomotion. The type of evolution is called adaptive radiation
This example is called homologous structures
These
Selective breeding
Domesticated animals are an example of fast-forwarded evolution
By selective breeding, favorable characteristics for humans were bred with a similar species to get offspring with similar characteristics
A dog, which is a domesticated wolf
Less aggressive wolves were bred until calmer offspring were produced.
Smaller wolves = smaller dog species
Fossil Records
Fossils are remaining of organisms found in stones that can help us determine their age and compare them to the currently living species.
It’s possible to determine the age of stones where fossils were found.
Bacteria are found in the oldest fossils, followed by algae, fungi and more complex organisms later.
Acanthostega is a fossil of vertebrae that doesn’t match any of the current living species, but shows similarities with them.
It has both 4 limbs that matches amphibians, but also a fish-like tail and gills which suggests it was probably a transition species between the fish and amphibians.
Melanism
A lightly colored species has a darker variant.
Biston betularia- peppered moth
Lightly colored moths blend with lightly colored tree branches avoiding predators
The melanistic form cannot blend in with the trees so are frequently eaten.
During the industrial revolution, the smog caused the trees to darken so the lightly colored moths became visible on tree branches and got eaten.
Melanistic form was less noticeable so had a higher rate of survival, and became more prevalent.
The switch from light population to dark population is an example of evolution
Shows how the species changes as a result of a changing environment by passing on its favourable genes.
Natural Selection
Charles Darwin was the first scientist to publish the theory of natural selection,
Alfred Wallace had the same idea at the same time was just too slow to publish.
Natural selection suggests that the better-adapted species will have a higher chance of survival.
Therefore be able to pass on their genes and the species will evolve
towards the better-adapted species.
Observation of Natural Selection
There are more organisms than the environment can support
Individuals must compete for natural resources in order to survive
Individuals in the same populations have different traits
These traits allow them to be better adapted to the environment
Individuals better adapted tend to survive to produce offspring with favorable characteristics
Sources of variation
Mutations - Orginal source of variation. New alleles are produced by gene mutation, which enlargens the gene pool of a population
Meiosis - produces new combinations of alleles by breaking up existing combinations in a diploid cell, crossing- over, and independent orientation of bivalents
Sexual Reproduction - Fusion of male and female gamete. Offspring have combination of alleles from the two individuals
Heritability and evolution
Organisms acquire characteristics during their lifetimes that are not heritable
Tennis players develop stronger and larger muscles and bones on their dominant hang because of being used intensely
Children of tennis player’s arms are the same size
Beak size of finches
Galapagos finches feed on seeds that fall on the ground, and for that, they have
specially adapted beaks.
The larger beaks are better for eating larger, harder seeds.
During the drought season, smaller seeds are not common, and only the large seeds are produced.
Between 1974 and 1977 there was a drought.
The finches with larger beaks tend to be better adapted to cracking bigger seedsand are more likely to survive.
The mean beak size during those drought years had increased, birds with smaller beaks couldn’t open the larger seeds and died.
During the rainy season in 1983, there were smaller seeds and the
animals with smaller beaks were faster to pick them.
They had an advantage compared to the ones with larger beaks.
The mean beak size again decreased, as now the better-adapted individuals were those with the smaller beaks, and they could breed and create more offspring.
Antibiotic Resistance in bacteria
Bacterial antibiotic resistance is a growing problem in the world.
Normally, the antibiotic resistance gene exists in organisms that naturally produce
the antibiotic.
This gene can be transferred to bacteria through the means of a plasmid.
The bacteria that have the gene cannot be killed by the antibiotic.
when administered to patients suffering from a bacterial infection, all the non-resistant bacteria will die, and the resistant ones will survive and multiply.
Since these bacteria can’t be killed by this type of an antibiotic, another antibiotic can be administered, killing this population, giving a selective advantage to the ones possessing resistance gene
In the end, only the resistant bacteria survive, multiply and exchange genes, leading to a broad range of ineffective antibiotics.
This can be avoided by limiting the antibiotic use, and by always taking the full dose, ensuring that all the non-resistant bacteria are killed and can’t acquire resistance genes from the resistant bacteria.
Binomial System
Universal system used to name the newly discovered species.
- First name is the genus name
- First letter of its genus is capital letter
- Second name is species name(First letter is lower case)
- If printed or typed a binomial is in italics
Dichotomous key
A tool that helps biologists distinguish between different organisms and classify
them correctly.
- key makes use of a series of statements about the features of an organism.
- These statements are numbered.
- Some statements lead to other statements that help better classify the organism.
- Other statements immediately give the name of the organism in question
- The species will eventually be named
Using Dichotomous Key
- Simple undivided leaves…………………..Elodea
Leaves forked or divided into segments………2 - Leaves forked 1 or 2 to form 1 or 3 …….. …………………Ceratophyllum
Leaves divided into more that four segments….3 - Leaves divided up into many flattened segments —-..———– Cambomba
Leaves divided up into many flattened segments……………………………………Myriophyllum
Using Dichotomous Key
Aquatic plants
- Simple undivided leaves…………………..Elodea
Leaves forked or divided into segments………2 - Leaves forked 1 or 2 to form 1 or 3
………………………………….Ceratophyllum
Leaves divided into more that four segments….3 - Leaves divided up into many flattened segments ……………………………….. Cambomba
Leaves divided up into many flattened segments……………………………………Myriophyllum
Classification
Is the process of grouping species.
Taxonomists- Biologists that specializes in classification
Artificial Classification
Classifying organisms based on one feature that they share, but disregarding all the other ways in which they differ.
i.e two groups of animals those with wings and those without wings
Natural Classification
Grouping organisms, based on
their ancestry.
This way of classification helps identification of species and is useful for prediction of their characteristics.
Three Domains
All organisms are classified into three domains. Archea-Archaeans, Eubacteria- bacteria & Eukaryota- Eukaryotes
Viruses are not classified into any domains as they are not considered living organisms
Taxon
A group of organisms, grouped by the means of natural classification.
Species are classified into a series of taxa
Each of which includes a wider range of species that the previous one, hierarchy of taxa
The 8 Taxa
Domain - Eukaryota Kingdom - Animalia Phylum - Chordata Class - Mammalia Order - Primate Family - Hominidae Genus - Homo Species - sapiens
Classification of plants Bryophytes – Mosses
- Have no real roots, but root-like hairs, rhizoids
- Simple leaves and stems
- No vascular tissues
- Reproduce using spores produces in capsules at the end of a stalk
Filicinophytes – Ferns
- Have roots, leaves & short non-woody stems
- Leaves are curled up in a bud & divided into pairs of leaflets- Pinnate
- Have vascular tissue
- Reproduce through spores produces in the sporangia, on the underside of the leaves
Coniferophytes – Conifers
- Shrubs & trees with roots, leaves and woody stems
- Narrow leaves with thick waxy cuticle
- Have vascular tissue
- Reproduce using seeds develop from ovules inside flowers ovaries
- Male cones produce pollen used for fertilization
- Fruits develop from the ovaries, to disperse the seeds
Angyospermophytes – Flowering plants
- Usually have roots, leaves and stems
- Trees and shrubs have a woody stem, others don’t
- Have vascular tissue
- Seeds are developed made from ovules inside ovaries in flowers
- Fruits, develop from these ovaries are used to disperse the seeds
Classification of animals
Porifera – Sponges
- No symmetry
- Attached to the surface
- No mouth or anus
- Contain pores
Cnidaria – Jellyfish
- Radial symmetry
- Tentacles and stinging cells
- Mouth, but no anus
Platyhelminths – Flatworm
- Bilateral symmetry
- Flat bodies
- Unsegmented
- Mouth, no anus
Annelida – Centipedes
- Bilateral symmetry
- Segmented
- Mouth and anus
- Bristles are often present
Arthropoda – Spiders and scorpions
- Bilateral symmetry
- Exoskeleton
- Segmented
- Appendages divided by joints
Mollusca – Snails
- Segmentations not visible
- Muscular foot and mantle
- Shell usually present
- Have a Mouth and anus
Chordata – Fish, mammals
- Notochord and dorsal nerve chord
- Dorsal nerve cord
• Post-anal tail
Further classification of phylum of chordata
Bony ray-finned fish
- Fish have fins supported by bones.
- Scales on skin
- Gills with one slit
- Fins supported by rays
- Swim bladder for buoyancy - so that they can change altitude in water
- External fertilization
Amphibians - Frogs
- Soft, moist & permeable skin
- Lungs withsmall internal folds
- External fertilization in water with protective gel
- Larva stage live in water
Reptiles - Crocodiles
- Dry scaly impermeable skin
- Lungs withextensive folds
- Internal fertilization with soft shells eggs
- One type of teeth
Birds
- Feathers on skin
- Lungs with parabronchi lungs
- Wings, instead of front legs
- Hard egg shells
- Beak, and no teeth
Mammals
- Hair on skin
- Lungs with alveoli
- Give birth to live young
- Mammary glands with milk
- Different types of kinds
Clade
- A group of organisms that evolved from a common ancestor.
- Anatomical features are rarely used as it hard to distinguish between homologous traits derived form a common ancestor and analogous characteristics developed by convergent evolution
- Base sequence of genes are used or corresponding amino acid base sequence
Cladogram
- Tree diagrams that shows the most probable sequence of divergence clades
- Cladograms have branching points, nodes
- In the 20th century, amount of base and amino acid sequence data & analytical power of computers grew exponentially
- Cladograms could be produces to show probable evolutionary relationships of large groups of spaces
- This has been used to re-evaluate the classification of many groups of organisms
Cladistics
Method of classification that analyses base and amino acid
sequence data to determine ancestry and construct cladograms.
Positive correlation between the number of amino acid sequences, and time since they split from a common ancestor.
Analogous traits
Those traits that have a similar appearance and function,
but have do not share the same origin
Analogous traits arise from convergent evolution, species of different origins, developed similar features in response to their environment.
The wings of birds and bats, which have the same function
even though the species developed these traits independently.
Homologous traits
Traits that are structurally different, but have the
same origin.
Homologous traits are a result of divergent evolution, a particular trait, shared by
many species, with structural differences as a response to the environment.
pentadactyl limb
Human classification through cladistics
- Mitochondrial DNA was used to classify humans and several other primates,using a cladogram.
- Mitochondria contain DNA, which is passed on from a mother to child, as it’s the mother gamete’s cytoplasm used for the first cell of the embryo development.
- There are base pair differences that can help us determine the time when
primate species diverged from each other. - 5 million years ago: Human-Chimpanzee
- 140,000 years ago: African-European/Japanese
- 70,000 years ago: European-Japanese
Reclassification of figworts
- Figworts were originally classified based on their structural differences.
- Sequencing of their genome showed that species within that family did not share a common ancestor.
- Some plants were moved to pre-existing families, plantain and broomrape
- Others were transferred to completely new families based on evidence of a split between species.
- Some pre-existing families were found to share the ancestor with figworts,
these families were all merged into one - With developments in computers’ analytical power and sequencing methods, there will probably be more and more re-classifications.
Cladogram analysis
Cladograms are constructed by plotting lines with node, representing points of divergence between species.
Lines are usually plotted against time and percentage difference in amino acid sequence, base pair sequence etc.
