BM108

RNA in origin of life

Replicating and enzymatic molecule

Endosymbiosis

Eukaryotic cells made from prokaryotic organisms via symbiotic relationships

Burgess Shale

Fossil deposit shows insight to early life (e.g. hallucigenia)

Evolution and Diversity of life

Diverse organisms come from simple ancestors over years

Evolution and genetic diversity

variations in DNA which natural selection acts upon

MRSA

methicillin-resistant staphylococcus aureus = bacterial infection which is resistant to antibiotics

Evidence supporting theory of evolution

fossil records, genetic similarities, observable changes in species over time

Fossil records

allows scientists to study changes over time

DNA in evolution

provides relatives among species and used in process of evolution

Gene pool

total genes in a population, collecting all genetic variations that can be inherited

Relationship between evolution and ecological niches

species evolved to occupy ecological niches, showing adaptability and diversity

Evolution and extinction

when species cant adapt to environmental change/competition, so ends

Random mutations

genetic variation, led to survival benefits and reproduction

Selection pressure

keeps species in check via competition for resources/environment challenges

Competition and evolution

- leads to natural selection, survival of the fittest for reproduction

Implications of antibiotic resistance in bacteria

- battle between bacteria and antibiotic treatments, influenced by selection pressure

Study early chemical life

Shows transition from non living to living systems on earth

Tidal locking

Moon rotates on it’s axis at the same rate it orbits earth, showing one face to earth

Clay in life theories

Stable environment for complex molecules to be made, act as a catalyst for life

Archaeopteryx

Shows reptile and bird like traits, birds came from reptile ancestors

Main models of evolution

gradualist and punctuated equilibrium model

Punctuated equilibrium

period of evolutionary stasis interrupted by period of rapid change

Fossil snake with remnant legs

shows gradualist theory

Molecular clock

number of protein/DNA sequence differences between 2 species at the time of shared ancestors

Genetics and biochemistry in related species

genetic code/DNA is universal, coding for similar proteins across species

ATP in evolutionenergy currency in different species

Homologous structures

anatomical similarities in species show common ancestor, e.g. forelimb bone on apes and whales

Speciation

new species arise, due to isolating mechanisms

Geographical isolation

population separated by physical barrier, leads to speciation

Microevolution

e.g. heavy metal tolerance in plants in lead mining areas

Industrial melanism

colour of moths from pale to dark from pollution, shows natural selection

Artificial selection

humans control evolution of species e.g. domesticated animals/crop plants

Selfish gene

genes act to ensure own survival/replication at expense of the organism

Sexual selection

natural selection when individual competes for mates, enhances reproductive success

Significance of Darwin's finches

exemplify adaptive radiation where species evolve different traits to fill ecological niches

Nature is a tinkerer, not an inventor

evolution modifies existing structure not creating new ones

Species

group of organisms that interbreed to make fertile offspring and are reproductively isolated from other species

Role of isolating mechanism in speciation

prevent interbreeding between 2 species, leads to new species developing

Galapagos islands in evolutionary studies

Darwin saw species on islands resembled mainland species but distinct differences, supporting natural selection

Impact of geographical isolation on evolution

lead to different evolutionary paths due to variety of environmental conditions

Importance of comparative anatomy in evolution

common ancestry via structural similarities among species

gene families in evolution

the mixing of functional modules to create new genes, leads to evolutionary diversity

Gametic isolation

reproductive isolation where gametes from different species cant unite to form zygote

Environmental pressure in microevolution

leads to changes in allele frequency within a population, driving evolution

Significance of cytochrome C gene in evolution studies

compare genetic differences providing insights to evolutionary relationships

Radiometric dating

used to establish the age of parent material via the amount of radioactive decay of radioactive isotope with a known half life

Founder of paleogenetic

svante paabo

What is paleogenetics

study of early humans and ancient populations using genetic methods

Project between 2006 and 2010 in paleogenetics

neanderthal genome project

Age limit for extracting ancient DNA from bones

430,000 as of march 2016

3 germ layers in metazoans

ectoderm, mesoderm, endoderm

Bilateral symmetry in metazoans

cephalisation = differentiation of a head with nervous tissue and sense organs

Coelomate body plan

body plan where the body cavity is within the mesoderm called the coelom

Significance of the notochord in embryonic development

defines the body axis and future site of vertebral column

Time period for Sahelanthropus

7 mill years ago

Brain size comparison of Ardipithecus to Australopithecus

Ardipithecus is smaller

Significance of Australopithecus afarensis

includes famous fossil 'lucy' and represents early hominin species

Time frame for homo baillis

2.1-1.5 million years ago

What distinguishes homo erectus in terms of brain size

notably enlarged brain compared to earlier hominins

time period for homo heidelbergensis

600,000-200,000 years ago

Percentage of non African modern humans' DNA derived from Neanderthals

4%-6%

Significance of the Denisovan genome

sequenced in 2010, divergence from Neanderthals occurred 640,000 years ago

When did homo sapiens evolve

300,000 years ago in Africa

2 main hypotheses in human migration

out of Africa and the alternative model

'gastrulation' reference to embryonic development

process that defines cell layers and body shape via rearrangement of epiblast layer

Pluripotent stem cells

give rise to any cell in animal body

Trophoblast during implantation

thickens and begins to implant into the uterine wall, forming the placenta

Inner cell mass (ICM) in embryonic development

forms embryo proper and crucial for development of the organism

Evolutionary significance of metazoan body plans

changed over evolutionary time allowing for specialisation and complexity in multicellular organisms

Traditional view of European origins

includes hunter-gatherers 45,000 years ago and farmer migrations from middle east 9,000 years ago

Latest view of European origins

Asian nomad 'ghost lineage' contributing to genome of modern Europeans

Neurulation

brain and spine formation, notochord induces a fold in the overlying epiblast/ectoderm, forming neural tube

Notochord signal induce in the ectoderm

signals the overlying ectoderm to become the neural plate

Somites

- repeating units form 40 pairs of body segments by end of week 4 development

Folic acid in pregnancy

- closure of neural tube and helps prevent conditions e.g. spina bifida

Spina bifida

condition caused by incomplete neural tube closure

3 regions the mesoderm differentiates into the next notochord

somites, intermediate mesoderm, lateral plate

Role of neural crest

form sensory nerve cells and other structures during development

Cell differentiation

pluripotent stem cells become specialized e.g. heart muscle or neurons

Morphogens

secreted molecules that induce cell fate decisions in recipient cells in a concentration gradient- dependent manner

Wolpert's 'French flag' model

shows cell sense the quality of morphogens and respond with specific differentiation based on programmed thresholds

Significance of SRY gene

gene on Y chromosome that controls male characteristics and promotes development of male reproductive anatomy

Homeotic genes

genes, when mutated, cause transformation of 1 body part to another e.g. drosophila mutants mixed body parts

Klinefelters syndrome

condition in males with XXY karyotype characterised by sterility, small testes and possible breast growth

Turners syndrome

condition in females with an XO karyotype resulting in short stature and failure to mature sexually

Default gonad development in absence of SRY

default development is female gonads

Tissue differentiation

local cell interactions/long range morphogen signals to organise tissue in a 3D embryo

What occurs in 1st trimester of human development

- early cell division, germ layer establish, start of organogenesis

What occurs in 2nd trimester of human development

- completion of organogenesis

Situs inversus

body organs are swapped, results in mixed left and right axis development

3 germ layers formed during development

ectoderm, mesoderm, endoderm

Role of cell responses to signals in development

initiate migration/specific differentiation processes that are irreversibly started

Significance of embryonic gonads being 'indifferent'

can develop into male or female gonads depending on presence of the SRY gene

Role or morphogen gradients in embryonic development

help establish body axes and influence cell fate decisions based on concentration levels

Transplanted cells in an embryo

adopt the form appropriate for their new location influenced by their original specification

Cell adhesion in tissue organisation

drives the sorting of cells into regional structures based on homophilic interactions

Outcome of non-disjunction during meiosis

results in sex chromosome abnormalities, can cause conditions e.g. turners

Relationship between HOX genes and body plan complexity

duplications of HOX genes have allowed higher organisms to develop more complex body structures

Spemann's organiser

region that induces nervous system, identified by Hilde mangold

Key molecules involved in neural induction

- BMP (bone morphogenic protein), BMP inhibitors, Chordin, Noggin, Follistatin

Role of BMP in nervous system

promotes development of epidermis, while BMP inhibitors from organizer induce neural tissue

The one before How is the ventral neural tube patterned

rostro caudal and dorsoventral

How is the ventral neural tube patterned

by sonic hedgehop protein secreted from the notochord and floor plate