Biology Evolution

Define organism

Any biological system that functions as an individual life form. All organisms are composed of cells

Define species

A group of individuals of common ancestry that closely resemble each other and that are normally capable of interbreeding to produce fertile offspring

Define population

Group of organisms of the same species in the same area

Define community

Populations of two or more different species occupying the same geographical area at the same time

Define variation

Differences between individuals of a species

List sources of variation within a species
Molecular:
Cellular:
Organisms:
Ecosystems:

genomes
specialised cells in multicellular organisms
speed of nerve impulses
between biomes

What is discrete variation + example?

traits that can be put into distinct qualitative categories
blood type

What is continuous variation + example?

Traits that vary along a quantitative continuum. Most biological variation is this.
Height

Compare variation within and between species

Intraspecies variation is within a species. Genetic variation mostly.
Interspecies variation is between species. Depends mostly on how closely related they are.

List sources of GENETIC variation within a species

Mutation in gene sequences
Gene flow: the movement of genes between different populations of organisms
Meiosis: crossing over, indepenant assortment and random orientation in forming sperm and egg cells
Sexual reproduction: random which egg with which sperm

Define species according to the morphological species concept

defined species by appearance. Body shape, colour, structual features. TRAITS.

Advantages of morphological species concept

applied to sexual and asexual organisms
works for extinct and fossilised species
Easiest and fastest to apply

Disadvantages of morphological species concept

relies on subjective criteria. may be disagreement
different indiivudals in a species may appear very different such as males and females

Define binomial nomenclature

first term indicates Genus
second term indicates species

State the four rules of binomial nomenclature formatting

genus begins with capital letter
species lowercase letter
italic, or handwritten is UNDERLINED
after first use fully, genus can be abbreviated to Capital first letter.

Outline why the binomial naming system is used in science rather than local names

reflects evolutionary relationships between organisms
enables scientist to talk to each other in the same language

Define species according to the biological species concept

group of actually or potentially interbreeding populations which are reproductively isolated from other groups
essentially can only interbreed to produce fertile offspring

Describe the limitations of the biological species concept, with mention of hybrids and geographical seperation
5 things

Naturally and artificially produced hybrids. eg mules, or peppermint between watermint and spearmint
Variations across geographical ranges
Divergence during speciation
Practical challenges of testing if reproduction is possible between groups
Asexually reproducing organisms/fossils

Compare and contrast morphological and biological species concepts

Define speciation

The process by which new species form, where one species is split into two or more species

Explain the difficulties in distinguishing between populations and species during speciation

Species typically exist in localised populations, which is difficult to define
Local populations are very important because they are a potential starting point for speciation. They share a gene pool before seperation
Development of barriers within local popluations are a possible cause of speciation
reproductive or physical barriers
This causes the accumulation of GRADUAL changes in the genotype over time, eventually forming new species.

Complete a case study in the difficulties distinguishing between populations and species in relation to the brown bear and polar bear

Interbreeding to produced fertile offspring “grolar” bears in rare cases
this challenges biological species concept in defining species
Genetically very similar, diverged around 500,000 years ago
Morphologically very different, despite genetic overlap, as they are both uniquely adapted for their environments, supporting morphological species concept for different species
very different ecological niches also supports this
they are viewed to be same or different species depending on which definition of species you use

Are chromosome numbers a distinguishing characteristic of a species?

yes

Explain why the typical number of chromosomes in a diploid cell is an even number

typically even, because chromosomes are arranged in homologous pairs, one from each parent

State the number of chromosomes in humans

23 pairs = 46

State the number of chromosomes in chimpanzees

24 pairs = 48

What are five features of chromosomes in eukaryotic organisms that are helpful to remember

no. is fixed per species
shape is a characteristic
occur in homologous pairs
genes occur at specific loci
chromosomes are copied precisely

Define karyotype

the number and type of chromosomes present in an organism

Define karyogram

a diagram showing the chromosomes of a cell, arranged in homologous pairs in descending order of size

list 4 characteristics by which chromosomes are paired and arranged on a karyogram

size, longest first
position of centromere
banding pattern
gene content

Define autosome

non-sex chromosomes

Define sex chromosome

determines sex rather than somatic charateristics

y chromosome is ___. x is ___. they appear on karyogram ____

short
long
last

evaluate the evidence for the hypothesis that chromosome 2 in humans arose from the fusion of chromosomes 12 (2a) and 13 (2b )with a shared primate ancestor

humans and chimpanzees
23 pairs vs 24 pairs
less than 3% of human dna is different to chimp
remarkably similar banding pattern between chimp 2a and 2b and human 2
human 2 has twos sets of centromeres, suggesting fusion of 2a and 2b, as usually only 1 centromere per chromosome
signicant sections of human 2 which are nearly identical to chimp DNA.
evidence supports fusion, unknown how though

define genome

the whole of the genetic info of an organism or cell

define gene

a section of DNA that codes for the sequence of a polypeptide

define allele

different base sequences of the same gene

Outline the cause of effect of a single-nucleopeptide polymorphism in genomes

single base substitution in a gene. most common mutation
usually found in non-coding region of DNA
SNP’s can act as biological markers, helping locate genes that are associated with diease
when snps occur within a gene, the may play a more direct role in a siease by affecting the genes function
therefore by studying snps, scientists can predict likelihood of disease/response to drugs
trace inheritance of disease within families

describe reasons why a larger genome doesn’t necessarily indicate presence of more genes

lots of DNA is degenerate and non coding

Compare variation within genomes sizes and gene sequences within and between species

within humans less variation than nonhuman human
size of a genome is the actual amount of genetic material, determined by base pairs
Base sequences of a genome determine determine how DNA is expressed

state the units for measuring genome size

base pairs (bp)
kilo b = 1000
mega b = 1000000
giga b = 1000000000

is there a relationship between the number of genes in a species and the species complexity in structure, physiology and behaviour

genome size varies between organisms
humans 3200mb
wheat 16 gb
larger genomes don’t necessarily confer with greater complexity
lots of plants, can form new species by combining whole sets of chromosomes called polyploidy. This results in extremely large genome sizes which have nothing to do with complexity

Define sequence in relation to genes and/or genomes

the specific arrangement and type of nucleotides in a gene

Have technological advancements sped the DNA sequencing process?
example

yes
Human genome project

List applications of genome sequencing. all of the human genome project

researching evolutionary relationships
personalised medicine
guide prevention, diagnosis and treatment of disease
advances in bioinformics and criminology
improved disease indentification
comparing modern vs ancient homo’s
allowed development of gene editing tech like CRISPR
enhance forensic science application

Discuss ethical considerations of genome sequencing

In criminology, if one persons genome is sequenced, it allows the idenfitication of human DNA (genome) for up to 5 generations forwards and backwards.
could lead to adoptive parent exposed, health insurance issues, matchmaking and job selection issues.

Explain how a new species can be formed abruptly by polyploidy

Define evolution

the change in the heritable characteristics of a population over time

Distinguish between lamarckism and darwinian evolution
lamarckism
darwinian

use and disuse: structures more frequently used will strengthen, develop and enlarge. opposite for non used structures
Inheritance of acquired characterstics: physical changes to the structures of an organism that result from use/disuse during their lifetime are inherited by offspring

natural selection mechanism
heritable variations (these are random) that benefits an individuals survival and reproduction are passed to offsring, so that voer generations, the frequency of the beneficial variation increases in the population

Outline evolution via natual selection as a paradigm shift in biology

we now understand that physica changes that occur during an organisms lifetime are not passed to offspring. Reproduction cells (germline) are seperate from somatic cells. Therefore only changes that affecct the germline can be passed on.

Are the similarities and differences between DNA, RNA and amino acids sequences evidence for evolution

yes

The rate of mutation of a gene is ___

fairly constant

What is the molecular clock

The number of differences between the sequence of bases of a gene in two species increases constantly over time

Example of protein to show the relationship between time, evolutionary relationships and biological sequences similarities between speioces

hamaeglobin. specific nitrogenous bases have changed between different organisms due to mutations

Define artificial selection/selective breeding

Selection in breeding carried out deliberately by humans to alter populations

What does artificial selection demonstrate?
artificial selection demonstrates ___

evolution occurs

List reasons why humans have selectively bred domesticated animals and crop plants

meat and milk in cattle
wool in sheep
Domestication of dogs and cats
increased food yield in crops

Explain an example of artificial selection in a crop plant

teosinte into corn/maize
corn is the result of artificial selection of wild grass called teosinte in mexico around 9000 years ago
selectively bread to produce fewer but larger ears
bred to grow from 2 kernels to 8-12
reduce stem branching
soften and enlarge kernel
no longer covering in hard casing

Outline how selective breeding can lead to rapid evolutionary change

overproduction of offspring for more variation opportunities
variation in heritable traits. occurs via meoisis, mutation and sexual reproduction
humans create selection pressure which affects survival/reproduction
differential survival/reproduction for those with wanted heritable trait
change in frequency of heritiable traits of population over time

Explain an example of artificial selection in a domestic animal

all dogs domesticated from a grey wolf ancestor
some 400 different breeds now exist as a result of selective breeding

Define homologous structure

similar structures that have evolved from a common ancestor to become adapted to different environments

Define Divergent evolution

occurs when organisms from a common ancestor accumulate differences over time as a result of exposure to different selective pressures in the environment, eventually forming new species

List examples of different types of homologous structures at different levels of biological organisation
anatomical structures:
Embryological patterns:
Metabolic reactions:
Molecular sequences:
Vestigial (remnants of) structures:

pentadactyl limbs
embryonic gills in reptiles, birds and mammals
use of glycolysis to derive ATP from glucose in nearly all forms of life
similar eye development gene in sharks flies and squids
remains of pelvis and leg bonds in snakes and whales

Define pentadactyl limb

Vertebrate 5 fingered limb plan found in tetrapods with the same general bond structure

Features of the pentadactyl limb
Identify pentadactyl limb structures
use the human arm as an example

Single proximal bone - upper arm - humerus
Two distal bones - forearm - radius and ulna
Series of smaller bones - wrist - carpals
Digits - fingers - metacarpals + phalanges

What is adaptive radiation

divergent evolution

is the pentadactyl limb a homologous or analogous structure

homologous

Describe how divergent evolution explains the pattern in pentadactyl limb structure yet allows for the specialisation of different limb functions

Same pentadactyl limb structure in humans, horses, bats, whales.
All evolved to be adapted and specialise for vastly different environments
horse metacarpals and phalanges fused for running on hard ground
whale elongated thick matacarpals and phalanges for long fin
Bat elongated thing ___ for flying

Define convergent evolution

Occurs when different species independently evolve similar traits or behaviours in response to similar environmental pressures

Define analogous structure

A feature with a similar function and superficial structural similarity, but different fundamental structure end evolutionary origin

State an example of an analogous structure found in two species

Wings
butterfly, insects and bat/bird have analogous wing structures
Common function but not inhereited from a flying ancestral species

Interpret cladograms to determine if traits are homologous or analogous

If common ancestor had the trait and passed it along to all of its descendants then the trait is homologous
If common ancestor didn’t have the trait, then the trait is likely analgous and independently evolved in the descendent species

Define speciation

The process by which new species form, where one species is split into two or more species

Compare the process of speciation with that of gradual evolutionary change in an existing species

Gradual evolutionary change over time is not speciation
Speciation results in the production of two genetically distinct species living at the same time
Gradual evolutionary change is a shift in the gene make up of one single species over time. Whilst this species may be distinct from its ancestor, it is considered the same species.

State the impact of speciation and extinction on the total number of species on Earth

rate of speciation increases the number of species on earth
rate of extinction (not constant) decreases

List two processes required for speciation to occur

Reproductive isolation
Differential Selection

Define reproductive isolation

For speciation to occur there must be barriers that prevent gene glow between the gene pools of two populations
geographic, behavioural, temporal

Outline geographical isolation between populations

occurs when barriers arise and restrict the movement of individuals (and their spores and gametes in the case of plants) between the divided populations
barriers can be natural or made by humans

Outline how reproductive isolation and differential survival lead to speciation

Once reproductively isolated, populations may experience different selection pressures. This leads to the differential survival of species with a desired heritable trait, from evolution via natural selection. Because distinct selection pressures, environments suited for different adaptations

Examples of different selection pressures in speciation

different climate
more or less competition for resources
different predators
different food sources

Outline the speciation between chimpanzees and bonobos
Must know it to these detail
Be able to use it as an example to explain the process of speciation

approx 1.8 million years ago, both bonobos and chimpanzees were the same species of apes on the North side of the congo river
It is hypothesised that the congo river which separated the north and the south side of the congo dried up, allowing part of the ape species to corss to the south during a 3-6 month period
Once it flooded again, the two groups were geographically seperated, as they couldn’t swim across the deep river. this resulted in the two groups being reproductively isolated
On the North side, the apes had to compete with gorillas for food, whereas the south side didn’t. This created a biotic interspecific differential selection pressure
It become advantageous for the North Apes to be aggressive, larger and stronger, whilst advantageous for the south apes to be smaller, docile creatures. Over time, due to natural selection, these traits were selected by the differing selection pressures, resulting in the differentiation of the apes into two different species. The larger agressive northernn chimpanzees and the smaller docile southern bonobos.

Define natural selection

Process where organisms better adapted to their environment survive and produce more offspring than competitors; the mechanism through which evolution occurs.

What is natural selection not?

It isn’t actually evolution. Its a theory by which the mechanism for evolution occurs.

Quick dot point summary of natural selection

Overproduction of offpspring
More variation
Selection pressure
Differential survival
reproduction of heritable trait
Increase in proportion of heritable trait over time

Has natural selection operated continuously over billions of years, resulting i the biodiversity of life?

Yes

Outline the observations and inferences that lead to the development of the theory of evolution by natural selection
2 ecological observations —> one inference
2 hereditary observations —> one inference
INFERENCE 3 NATURAL SELECTION
This is inductive reasoning

Populations can increase exponentially but usually remain a constant size
limited natural resources
Not all offspring that are produced will survive and reporduce because of a struggle for resources

Individuals in a pop vary in many characeteristscs
Many of these are heritable and passed on to offspring
Some individuals are more likely to survive and reproduce than others because of their heritable traits

Outline the theory of evolution by natural selection as an example of correspondence, coherence and pragmatic theories of truth

Outline the requirements for evolution by natural selection

overproduction
variation: meiosis, sexual reproduction, mutations
Resource limit
Selection pressures, biotic or abiotic
Differential survival/selection: survival of the fittest
Reproduction of heritable genes
Change in the gene frequency, increased

Explain why natural selection can only function if there is variation in a species

species cannot evolve by natural selection without variation in the heritable characteristics
The more variation, the more effective the traits will be selected for

Name the three sources of genetic variation

mutation
meiosis
sexual reproduction

Outline the source of genetic variation of mutation

Mutations are errors in copying (snp) the genetic information during DNA replication, resulting in alleles
Mutations introduce new alleles
if these mutations are in the germline cell, they can be passed on to offspring and are heritable

Outline the source of genetic variation of meiosis

Crossing over of segments of individual maternal and paternal homologous chromosomes results in new combinations of genes
Independent assortment of paternal and maternal chromosomes in meiosis
Random orientation of maternal and paternal chromosomes

Outline the source of genetic variation of sexual reproduction

Random fusion of sperm with random egg results in even more random zygote
this produces NEW COMBINATIONS of alleles, as random which goes with which

Do species have the ability to produce more offspring than the environment can support

Yes
This is a key part of natural selection

Use an example to illustrate the potential for overproduction of offspring in a population

A female elephant can have an average of 6 offspring during her lifetime. If all survived, there would be 19 million elephants in 750 years

State two evolutionary benefits of overproduction of offspring

Overproduction of offspring increases the odds that at least some of the offspring will survive to adulthood, required for the continuity of the species
Overproduction of offspring ensures there is ample genetic variation in the population should the species need to adapt to changing environmental conditions

Define carrying capacity

Max no. of one species that an ecosystem can support

Compare direct and indirect competition. use an example for both
Direct:
indirect:

when one individual directly affects anothers ability to obtain resources
male elk will use aggression to demonstrate dominance and to prevent other males mating with females

When individuals indirectly compete for resources, such as territory, light or prey
grizzly bears catching a salmon so that the salmon can no longe rbe eaten by bears at different points along the river

List examples of resources that may limit population size

food, water, shelter, space, and access to mates

Is consequence of overproduction of offspring that there is a competition for resources
use example

yes
galapogas finches