B4 - Natural Selection and Genetic Modification

Darwin's theory

Evolution by natural selection

Stages of natural selection

mutation causes Variation in population, adaptation due to selection pressure, reproduction, allele passed on, cycle repeats and allele frequency increases

Evidence for human evolution

Fossils and stone tools

Fossil from 4.4 million years ago

Ardi

Fossil from 3.2 million years ago

Lucy

Discoverer of fossils from 1.6 million years ago

Leakey

Stone tools production method

By hitting a stone with another to knock off chips

Dating methods for stone tools and fossils

Comparison, analysis of complexity, rock layer, carbon dating

Use of rock layers in dating

Deeper layers indicate older fossils/tools

Five kingdoms in classification

Animals, plants, fungi, protists, prokaryotes

Protists definition

Eukaryotic single-celled organisms

Prokaryotes definition

Single-celled organisms without a nucleus

Three domains in classification

Archaea, Bacteria, Eukaryota

Archaea definition

Primitive bacteria usually living in extreme environments

Eukaryota kingdoms

Protists, fungi, plants, animals

Reason for three domain system

Genetic analysis and DNA sequencing

antibiotic resistance

population of bacteria encounter antibiotics. mutation occurs, those who survive reproduce making a resistant population

continuous variation

variation between a range - height or weight

discontinuous variation

variation with fixed possibliites- eye colour

continuous variation graph

bell shaped curve

how to prevent antibiotic resistance

use full prescription time, don’t use for virus, don’t over prescribe, better hygiene

how does penicillin affect bacteria

stops it making cell wall so it can’t divide - doesn’t effect humans- no cell walls

binomial naming system order

kingdom, phylum, class, order, family, genus, species

evolution

change in the frequency of a phenotype in a population over many generations

why do we see really resistant bacteria

overusing antibiotics, not using full course, poor hygiene

general trend for human evolution

increase in height and brain capacity. Straighter toes and shorter arms

speciation

when a specie is separated due to a geographical barrier and evolves over time so much due to different selection pressures that the offspring of those species are infertile and now they are different species

pentadactyl limb

limb with 5 digits

Wallace discovery

some catepillars evolved to be red and bitter or poisonous. Birds learnt to avoid red caterpillars. Other insects evolved to be red and birds avoided them in fear that they were poisonous or bitter

how does the pentadactyl limb prove evolution

we see the pentadactyl limb in various species with different functions. This similarity provides evidence that species with this limb evolved from the same ancestor due to similar bone structure

who created the binomial classification

carl linnaeus

kingdoms in domain bacteria

eubacteria

kingdoms in domain archaea

archaebacteria

evidence for evolution

pendactyl limb, fossils

significance of Lucy’s fossil

she could walk on two legs , suggesting humans adapted to be able to walk on 2 legs

why were Darwins theory of evolution more widely accepted

fossil discoveries , better development in genetics field

why are fossil records incomplete

fossils can be damaged, soft tissue doens’t form fossils

what are bacteria

single celled organisms without a nucleus

ardi fossil features

short legs , long arms, long curved toes, small brain

Lucy fossil features

normal toes, larger brain than ardi , shorter arms than ardi, longer legs than ardi, taller than ardi

Leakey fossil features

bigger brain than Lucy, short arms, longer legs, taller , normal toes

what did Darwin do

voyaged the world and studied plants and animals and observed variation within species.

developed the theory of evolution by natural selection

what did Darwin conclude whilst studying plants and animals worldwide

those best suited to the envionment were more likely to survive and reproduce

what did Wallace do

independently developed theory of evolution through natural selection

published papers with Darwin

what did Wallace study and develop

studied warning colouration in species and developed the theory of speciation

what have the contributions of Darwin and Wallace to evolution helped us understand

all life forms change through evolution, all life forms have descended from a common ancestor

how have the contributions of Darwin and Wallance to evolution helped modern biology

classification is more accurate and based on how closely related species are,

improving conservation due to realisation that genetic variety is needed for species to adapt to selection pressures

antibiotic

kill bacteria by disrupting their cell functions

what cant antibiotic be used for

viruses

why don’t antibiotics work on viruses

antibiotics target bacterial cells but viruses don’t have cells

how do ardi , Lucy and Leakey prove evolution

their changes overt time suggest evolution to adapt to new selection pressures

how do stone tools prove evolution

more complex tools over time suggest that human brains have become larger

how were organisms traditionally classified

According to similarities and differences in observable characteristics. 5 kingdom

selective breeding

when humans artificially select the individuals with desirable characteristics and breed them together

selective breeding steps

• select organism with desirable characteristic

• breed them together

• select best of offspring and breed them

• repeat over several generations

examples of selective breeding for animals

cows that produce more milk and meat, chicken with larger eggs, dogs with more gentle nature

example of selective breeding in plants

more disease resistant and weather tolerant plants

increased yield and size

better taste and prettier flowers

uses of selective breeding

• agriculture - cows with higher yield

• medical research - breeding best animals for testing

tissue culture

the growing of cells or tissues on an artificial growth medium

plant tissue culture

• remove tissue from roots or shoots

• under aseptic conditions, the tissue is transferred to sterile petri dish with nutrient agar and it grows into a callus

• hormones like auxin added and cells grow into plantlets

• plantlets are transferred to plotting composts

why are the tissue pieces transferred to the sterile Petri dish under aseptic conditions

to prevent the growth of microbes that may harm the plant

what can selective breeding cause

leads to inbreeding which can lead to a reduction in the gene pool.

what are some applications of plant tissue culture

growers can clone their best plants

prevent extinction of rare plants by cloning

helps grow plants that are difficult to grow from seed

how is plant tissue culture useful for growers

they can grow plants cheaply, quickly in a small space with great yield and at any time of year

animal tissue culture

• sample of tissue is extracted from animal

• enzymes are used to separate the cells that make up the tissue sample

• the cells are places in a culture vessel and bathed in a growth medium

• once the tissue culture is grown, it can be stored for future use

why are the tissues added to a growth medium

contains all the nutrients needed for cells to grow and multiply into tissues

What is animal tissue culture used for

Medical research . You can carry experiments on tissues in isolation

What does working on tissues in isolation prevent

Complications from other processes in the whole organism when investigating the effects of substances or environmental change .

genetic engineering

modifying the genome of an organism to introduce desirable characteristics .

how does genetic engineering modify the genome of an organism

removing or altering genes within that organism or inserting genes from another organism

what do you call organisms that receive the genetic material

genetically modified organisms , transgenic organism

recombinant plasmid

plasmid with hybrid dna as it has the foreign dna incorporated in the plasmid

what can crops with additional vitamins be used to try prevent

vitamin deficiencies in some regions

use of genetic engineering in medicine

gene therapy, genetically engineering bacteria to produce human insulin

gene therapy

replacing faulty genes that cause inherited diseases with working versions of those genes

restriction enzymes

used to isolate and cut out required gene leaving it with ‘sticky ends’

what do sticky ends mean in terms of genes

a section of unpaired bases

how can you genetically modify bacteria to produce insulin

• extract DNA of an insulin producing gene and identify and extract the insulin gene with restriction enzymes

• extract plasmid DNA from bacteria and extract some genes with restriction enzymes cutting the plasmid open

• join the cut plasmid and insulin gene with ligase enzyme to make recombinant plasmid

• put recombinant plasmid back in cell

what else is engineered in insulin producing bacteria to try identify the successful cells

the gene for antibiotic resistance is also added by same process. allow bacteria to grow in a dish and add antibiotics. those that survive can produce insulin.

how can you then duplicate the bacteria that produce insulin

place in a fermenter so they reproduce quickly

what is a vector in terms of genetic engineering

something used to transfer dna into a cell

what are the types of vectors

plasmids which can be transferred between bacteria, viruses - inject DNA into infected organisms

what modern technology has increased food supply

agricultural machinery , fertilisers, insecticides and herbicides, selective breeding, GM Crops

how has agricultural machinery increased food supply

replaces humans and improved efficiency

how do fertilisers increase food supply

increase amount of nutrients meaning plants can grow larger

how do Insecticides increase food supply

they kill off unwanted insects meaning less damage to plants

how do herbicides increase food supply

kill weeds and reduce competition meaning plants can grow more

how does selective breeding increase food supply

breeding animals and plants that produce large yield mean the offspring produce high yield

how do GM crops increase food supply

they are genetically modified to increase yield

how can plants be genetically modified

resistant to pests and herbicides, enriched in vitamins

effect of plants resistant to pests and herbicides

increases productivity and yield

BT crops

crops genetically modified with a BT toxin from a bacteria which produces toxin in stem and leaves - kills insects

what is the effect of crop plants being modified to be resistant to herbicides

herbicide only kills weeds. increased yield and efficiency

what do crops with additional vitamins aim to do and give me an example

improve nutritional value and prevent deficiency diseases in certain regions of the world. golden rice

golden rice

has genes from another plant and bacterium. produces a chemical that is turned into vitamin A in human body.

what are negatives of BT crops

unknown effect on consumers, resistance may develop in pests, could affect food chain

positives of BT crops

minimises need of pesticides, less non-pest insects harmed

alternative methods of increasing crop yield

biological control , fertilisers

biological control

using the pests own natural predators to control the pests

fertilisers

substance with high amounts of nutrients and minerals for growth