Exploring Biomedicine Exam Revision

wing evolution

• evolved from gills and from structures that would help gliding

• early wings aid locomotion across water surfaces (evidence from stoneflies)

• wiggle → glide→ flap + glide→ jump + flap

adaptations to flight

• low bone density

• enlarged chest muscles

• feathers

• air sacs in body connecting to lungs, can extract more oxygen per breath

archosaurs

• ruling reptiles

• not a monophyletic group

• birds + crocodiles + dinosaurs + reptiles

evidence for the evolution of bird from dinosaurs

feathers and wings in dinosaur fossils

sprawling animal movement

• in one plane, side to side

• crocodile, lizard

upright animal movement

• change from sprawling to upright enables quicker locomotion

• back to front plane of movement

• mammals move the back half of the body forward and back

• dolphins and whales swim in this way also

• crocodiles can do upright movement when moving fast to catch prey, but their body structure isn’t well suited to this

asexual reproduction

One parent produces offspring without gametes.

sexual reproduction

2 haploid gametes combine to form one diploid zygote.

types of asexual reproduction

• fission

• budding

• fragmentation

• parthenogenesis

• spore formation

• vegetative propagation

fission definition

form of asexual reproduction in which an organism divides equally into two or more genetically identical offspring.

Binary fission - 2 organism result -common in Bacteria and Archaea

Multiple fission - more than 2 cells produced - common in Protista

Fission Domains/Kingdoms

all Domains/Kingdoms of life

Budding definition

two unequal parts

bud/outgrowth forms on parent cell and breaks off to form daughter cell

occurs in multi and unicellular organisms

eg: hydra

Budding Domains/Kingdoms

All domains/kingdoms of life

Fragmentation

fragments of the organism break off to form a new organism

eg: flatworm

Fragmentation Domains/Kingdom

Not all domains, only in the eukaryotic kingdom

Parthenogenesis

unfertilised egg develops into an individual

females only, mostly they can reproduce sexually as well

eg: lizards, fleas, wasps, bees

Parthenogenesis domains/kingdoms

only in Animalia

Vegetative propagation

new plant grows from a fragment/cutting of a parent plant

Vegetative propagation domains/kingdoms

only in Plantae Kingdom

Anaerobic respiration

organisms that use another input for cellular respiration instead of oxygen, eg: hydrogen sulfide, methane

Respiration in Microbes (Bacteria and Archaea

can do aerobic (obligate aerobic), anaerobic (obligate anaerobic) or both (facultative anaerobic)

Respiration in Fungi

• can do either aerobic or anaerobic, mostly aerobic

• use hyphae to get oxygen from small air pockets in soil

Respiration in plants

• mainly aerobic

• obtain oxygen via diffusion through stomata or lenticels

• stomata in the leaves or stems

• lenticels in woody stems and some roots

• use pneumatophores (aerial roots) in anoxic/waterlogged soil

• also have aerenchyma for gas exchange from exposed to submerged parts of the plant

pneumatophores

Specialized roots found in certain plant species, such as mangroves, that grow above the ground to facilitate gas exchange in waterlogged soils.

aerenchyma

Specialized plant tissue that allows for the exchange of gases, such as oxygen and carbon dioxide, in aquatic plants. It consists of large air-filled spaces within the plant's tissues, aiding in buoyancy and facilitating gas diffusion.

types of gas exchange systems in animals

• direct diffusion

• integumentary diffusion

• trachea

• gills

• lungs

trachea

• system of tubes for gas exchange found in insects

• opening of tubes = spiracles

• tracheal system separate to circulatory system

• needed because the external surface is impermeable to oxygen

• some insects use muscle contractions to ventilate

gills

• found in fish, molluscs, annelids, crustaceans

• can be in a cavity or external

• highly branched/folded for high SA:V ratio

• water passes through and diffuses into circulatory fluid/coelom

• use countercurrent flow to maximise the O2 concentration difference between internal fluid and water across the entire length of the membrane - this maximises oxygen absorption

lungs

• found in amphibians, birds, reptiles and mammals

• vary greatly across the animal kingdom

amphibian lungs

simple, sac-like

reptile lungs

vary, but generally sac-like and sometimes sub-divided

mammal lungs

branching, end in air filled sacs (alveoli)

Bird lungs

parallel series of tubes (parabronchi)

autotrophs - kingdoms and domains

• found in all 3 kingdoms

• only in bacteria, archaea, protista and plantae

heterotrophs - kingdoms and domains

• found in all kingdoms

• exclusively in animalia and fungi

autotroph adaptations to living on land

• roots to extract water and nutrients from soil

• vascular tissue for water + nutrient transport

• water resistant cuticle to minimise water loss

• tissue for structural support

• diversity of leaf types and size for photosynthesis

importance of roots

• uptake of water and nutrients

• anchorage and support as plant size increases

• synthesis of plant hormones

• storage of nutritional reserves

• modified for environment (ie: aerial for marsh and swamp, clasping for climbing, prop for support and contractile to pull)

Vascular system

• allows for increased size

  • allows transport of water and sugar to larger areas

  • lignin prevents xylem collapsing under hydrostatic pressure

heterotroph feeding strategies

• filter feeding

• parasitism

• diversity of mouthparts - invertebrates

evolution of jaws

• derived from gill arches in fish

• once jaws evolved, teeth follow

• evolution of jawed fish = decline in marine invertebrates (eg: trilobites)

how does excretion regulate the internal environment

• controls cell/body water content

• maintains solute composition

• remove metabolic waste products and other unwanted substances

elimination vs excretion

excretion is removal of waste products, elimination is removal of stuff that has never been a part of the body - ie unabsorbed food

passive excretion

• common in bacteria and fungi, some aquatic plants

• solutes cross the membrane without specific transport protein

• movement occurs due to chemical gradient - through osmosis and diffusion

active excretion

• specialised cells or organs for excretion and elimination

• allows for larger, more complex organisms

flame cells

• specialised excretory cells

• found in freshwater invertebrates

• function like the mammalian kidney - remove waste materials

• bundle of flame cells = protonephridia

coelom definition

A body cavity that separates the body wall from the internal organs, providing space for organ movement and protection.

coelom importance

• fluid filled - internal support

• separates internal processes from gut

• allows transport of fluids (circulatory and excretory systems)

• space for development of internal organs

• enables increased body size

excretion - protists and early unicellular eukaryotes

• no specialised organs

• majority of waste products eliminated by passive diffusion and osmosis

• active transport through specialised membrane channels or exocytosis

• eg: amoeba use exocytosis to remove waste product post-phagocytosis

fungi excretion

• no specialised organs

• some use of passive diffusion/osmosis

• active transport through specialised membrane channels or expelled directly using contractile vacuoles

plant excretion methods

• transpiration - gaseous waste and water through stomata, lenticels and outer stem or fruits

• guttation - drops of xylem sap gather on tips/edges of leaves on some plants at night when stomata are closed and water builds up

• storing - some organic waste stored in cells in bark, stems and leaves that eventually fall off

• diffusion - metabolic waste excreted via diffusion into soil(terrestrial)/water(aquatic)

Nitrogenous waste forms

• Ammonia (1N)

• Urea (2N)

• Uric Acid (4N)

• Guanine (5N per molecule)

Ammonia excretion pros and cons

• very toxic

• requires lots of water

• extremely soluble

• no energy expended in synthesis

Urea excretion pros and cons

• less toxic and less water required for excretion than ammonia

• more complex synthesis

• costs 4ATP per Urea molucle

Uric acid excretion pros and cons

• highly insoluble

• non-toxic

• excretion conserves water

• more complex synthesis with higher metabolic cost

• takes 24ATP per molecule

Guanine excretion pros and cons

• nearly insoluble

• excreted with little water loss

• high energy cost

excretory organs listed

• simple protonephridia (marine worms)

• complex nephridia (earthworms and some insects)

• Malphigian tubule system (many insects and spiders)

• Hindgut (insects, birds and reptiles)

• liver and kidney (vertebrates)

challenges of living on land

• oxygen is in air = need mechanism of capture

• lack of water = dehydration and dessication

• UV radiation = DNA and cell damage

• no support = need structure to support you

• energy hungry = passive movement limited

• complex and varied terrestrial ecosystems = need specific adaptations to survive

structures for active movement on land

• cell walls

• vascular tissues

• lignin and bark

• seeds/spores

• legs

passive movement pros and cons

organisms can move passively largely through air or water, but some species (parasites, spores or seeds) can attach themselves to hosts

• pros: little or no energy expenditure

• cons: little or no control over final location - could end up in suboptimal environment.

active movement pros and cons

movement under the organisms own control that requires their own energy.

• pros: more control over where they move to

• cons: must balance resources for movement against needs for cellular maintenance and reproduction

movement in water pros and cons

pros:

• support (heavy organisms are supported)

• hydration (no issue with desiccation)

• nutrient rich environment

• environmentally buffered (stable temperature and pH)

cons:

• strong currents (might end up in suboptimal locations)

• buoyancy (maintaining position requires energy and/or specialised structures

• water levels might fluctuate (evolution of land species)

structures for movement in water

• cilia and flagella

• feet-like projections

• fins and flippers (bird and mammals)

pros and cons of movement in air

pros:

• safest environment

cons:

• need specific adaptations to fight gravity and ensure lift

• strong wind currents can take you to suboptimal environments

• extremely energy hungry - need enormous muscles

wing evolution

• evolved from gills and from structures that would help gliding

• early wings aid locomotion across water surfaces (evidence from stoneflies)

• wiggle → glide→ flap + glide→ jump + flap

adaptations to flight

• light (taken by the wind anyway)

• produce lots of seeds (chance of landing in an optimal environment is low)

• large surface area for lift (eg: helicopter seeds, wings, gliding membranes)

• low bone density

• enlarged chest muscles

• feathers

• air sacs in body connecting to lungs, can extract more oxygen per breath

Archosaurs

• ruling reptiles

• not a monophyletic group

• Birds (should be included) + crocodiles + dinosaurs + reptiles

evidence for the evolution of bird from dinosaurs

feathers and wings in dinosaur fossils

sprawling animal movement

• in one plane, side to side

• crocodile, lizard

upright animal movement

• change from sprawling to upright enables quicker locomotion

• back to front plane of movement

• mammals move the back half of the body forward and back

• dolphins and whales swim in this way also

• crocodiles can do upright movement when moving fast to catch prey, but their body structure isn’t well suited to this

early adaptations for active movement

• Cilia (tiny hairs that cover the outside of the cell)

• Pseudopods (temporary arm-like projections of a eukaryote membrane) that move out in specific directions

• Flagella - longer hair-like structure that is propelled around

early adaptations: cilia

• tiny hairs that beat in a coordinated movement across the cell

• unicellular species that use cilia tend to be:

  larger and faster than those that use a flagellum

• comparable structures in animals: larval phase of marine annelids and most molluscs (slugs and snails) use cilia to move through water

early adaptations: pseudopods

• unicellular amoebae

• alter cell shape by pushing cytoplasm outwards

• can have multiple pseudopodia projecting in different directions

• can use this to move in a particular dimension

• when food is in scarce supply amoebae congregate to form a single travelling colony (as multiple cells or one massive cell)

• comparable structures in animals:

  • parapodia (leg-like structures) in marine worms which are paired fluid-filled appenFadages that assist with movement, but have nervous control

Early adaptations: Flagella

• whip like appendage protruding from cell body of prokaryote and eukaryote bacteria

• for locomotion along a single plane

• can also function as a sensory organelle

• comparable structure: larvae of sponges and majority of animal sperm have flagellae

active propulsion - cephalopods (some molluscs)

take in water through mouth then contract body to push water through their funnel to achieve forward propulsion

how do tentacles aid in movement

• act as pseudo-legs when not swimming

• control direction of propulsion

• assist when walking on land

Annelid movement

in water: marine worms

• free swimming and sedentary

• unjointed leg-like parapodia/chaetae on every body segment

• trocophore larvae = free swimming ciliated larva

on land: earthworms

• mostly terrestrial

• live in soil

• feed on organic matter

• grow very long up to 3m

• react to vibrations

Chordate features

• vertebrates are a subphylum of chordates

• all chordates have:

  • notochord

  • dorsal nerve cord

  • myomeres (segmented muscles)

• early chordates (fish) have:

  • gill slits

  • post-anal tail

cartilaginous vs bony fish

cartilaginous:

• earliest fish had a cartilaginous skeleton (sharks and rays)

• large liver filled with low density oil to aid buoyancy, but still must swim to maintain it

• cartilage lighter than bone

• pectoral fins for dynamic lift

bony:

• swim bladder (closely related to lung) for buoyancy

both:

• move using caudal tail and fins

• active muscle-assisted movement

• maintain buoyancy to save energy

first tetrapods

• lobe-finned fish evolved bones to walk/paddle in shallow water

• early amphibians had gills and lungs - some used swim bladder as a lung on land

• today amphibians still need water to reproduce, since tadpoles have gills but adult frogs have lungs

change from quadruped to bipedal

• big toe reduced

• pelvis shortened, more bowl-like to support base of spine

• femur bends inwards, knee straightened, patella central to joint

• foramen magnum on the underside of the skull

• less robust upper arms

what is a fossil

The preserved remains or traces of ancient organisms found in rocks or sedimentary layers.

what increases likelihood of fossilisation

• bones or hard structures

• quickly covered by sediment after death

• anoxic environment

• chemistry of the environment doesn’t dissolve the organism

relative dating of fossils

• stratigraphy - ordering by the order of rock layers from oldest to most recent

• use of index fossils - fossils found nearby that have a known date

absolute dating

radiometric methods - based on level of decay of different elements depending on the time scale

what can fossils tell us?

• dates

• physiology

• diet

• reproductive mode

• movement

• migration

• development

• thermoregulation

• colour

• behaviour

major evolutionary transition

changes in the way information is stored and transmitted

involve new units of reproduction, division of labour and development of more complex units

eg: evolution of the genome, evolution of multicellularity, evolution of eukaryotes, evolution of eusociality

adaptive radiation

The process where an evolutionary lineage undergoes rapid diversification into a variety of lifestyles or ecological niches

usually involves exploitation of a new environmental niche in the absence of competition

mass extinction

statistically significant departure from background extinction rates resulting in a substantial loss of diversity.

end ordovician mass extinction

• first global cooling and glaciation, causing decreased sea levels, loss of shallow water habitats and change in ocean chemistry

• then global warming with rise in sea levels and change in ocean chemistry

• nearly 85% of marine species lost within 3.5-1.9 million years

end triassic mass extinction

• increased extinction and decreased origination rates

• increase in volcanic activity → increase in atmospheric CO2 → increase in temperatures and a calcification crisis in the ocean

why are we heading for a 6th mass extinction

• our extinction rates now are higher than background extinction rates

• current extinction rates are comparable to previous mass extinction events

human causes of extinction

• habitat loss

• species introduction

• pollution

• overexploitation

• climate change

  • increase in atmospheric CO2

  • increase in ocean acidity (affects calcifying marine life)

  • increase in temperature

what is the Anthropocene?

The Anthropocene is a proposed epoch defined by human impact on Earth's ecosystems. It signifies when human activities became the primary force shaping the planet, including industrialisation, deforestation, and climate change.

evolution

cumulative change in a population or species over time

adaptation

an inherited aspect of an individual that allows it to outcompete other members of the same population - traits that have evolved through the mechanism of natural selection

when can adaptation occur

• when environments change

• when some individuals carry an advantageous genetic variation

• when species survive long enough to adapt

• when the trait/DNA variant is passed down from parent to offspring

microevolution

studies the evolutionary agents of change that shape the genome of a species

involves changes in the frequency of alleles within a species or small group of organisms

species definition

groups of actually (or potentially) interbreeding natural populations that are reproductively isolated from other such groups

Microevolution: Agents of change listed

• natural selection

• mutation

• sexual reproduction

• genetic drift

• gene flow

natural selection

Process where individuals with advantageous traits are more likely to survive and reproduce, leading to a gradual change in the genetic makeup of a population over time.