Evolution and life diversity Flashcards
1
Q
Why reproduce?
A
-All species reproduce and pass on their genetic material to the next generation, otherwise the species would die out.
• Reproduction can occur either with a partner or without a partner. This characteristic can be used to classify reproduction methods.
2
Q
different ways that organisms can reproduce
A
1) Asexual reproduction: A mode of reproduction where an organism can replicate itself without another organism.
2) Sexual reproduction: A mode of reproduction involving the fusion ofone haploid gamete with another haploid gamete to create a diploidzygote.
3
Q
Sexual reproduction evolution
A
- 4 billion years ago: first life
- 3.5 billion year ago: photosynthetic bacteria
- 2 billion years ago: origin of eukaryote and multi cellular eukryote
- 1 billion year ago: meotic sex
4
Q
Asexual reproduction
A
Asexual reproduction is found in all Domains and all six Kingdoms of life
(Bacteria, Archaea, Protista, Fungi, Plantae, Animalia).
There are several different types of asexual reproduction:
1. Fission
2. Budding
3. Fragmentation
4. Vegetative propagation
5. Spore formation
6. Parthenogenesis
5
Q
Sexual reproduction
A
Sexual reproduction is found only in the four Eukaryote Kingdoms of life (Protista,
Fungi, Plantae, Animalia).
Sexual reproduction differs greatly among species:
6
Q
Asexual vs Sexual reproduction
A
Asexual reproduction
-Requires only one parent organism
-Offspring are genetically identical to parent, therefore diseases are passed on and adapting to new conditions (i.e. evolution) is very slow
-Time and energy efficient, e.g. don’t need to find a mate
-The population can increase rapidly when conditions are good
Sexual
-Requires two parent organisms
-Produces genetic variation in offspring, therefore the species is more able to adapt to different environments or a population may be more resistant to disease
-Requires more time and energy, e.g. need to find a mate
-Generally much slower because more time/energy required and only half the population can reproduce
7
Q
Fission
A
Fission is found in all Domains and all Kingdoms of life
(Bacteria, Archaea, Protista, Fungi, Plantae, Animalia).
• Occurs in unicellular and multicellular organisms.
• A parent cell or organism divides itself into equal parts.
1) Binary fission results in two cells or organisms
(common in Bacteria and Archaea).
2) Multiple fission results in more than two cells (common
in Protista)
8
Q
Budding
A
Budding is found in all Domains and all Kingdoms of life (Bacteria, Archaea, Protista, Fungi, Plantae, Animalia).
• Occurs in unicellular and multicellular organisms.
• A parent cell or organism divides itself into two unequal parts.
• A small bud (outgrowth) forms on the parent cell or organism and breaks off to form a new daughter cell or organism.
9
Q
Fragmentation
A
Fragmentation is found in all Eukaryote Kingdoms of life
(Protista, Fungi, Plantae, Animalia).
• Occurs in multicellular organisms.
• Fragments of an organism can break off and then
become into a new organism.
10
Q
Vegetative propagation
A
Vegetative propagation is found in one Eukaryote Kingdom of life (Plantae). • Occurs in multicellular organisms. • Where a new plant grows from a fragment of the parent plant. • Many different strategies, such as: • runners • bulbs • tubers • suckers/basal shoots/root sprouts
11
Q
Spore formation
A
Spore formation is found in three Eukaryote Kingdoms of life (Protista, Fungi, Plantae).
• Occurs in unicellular and multicellular organisms.
• A parent plant forms hundreds of reproductive units, called spores, which may be stored in a casing until they are released.
• Spores allow for dispersal of the organism to new locations.
• Spores can grow into a new individual without requiring fertilization.
• Many organisms that reproduce via asexual spores can also reproduce sexually
12
Q
Parthenogenesis
A
Parthenogenesis is found in the Eukaryote Kingdom of
Animalia.
• Occurs in multicellular organisms.
• An unfertilized egg develops into an individual.
• Occurs in water fleas, wasps, bees, ants and some fish
and lizards.
• Most organisms that reproduce by parthenogenesis
can also reproduce sexually
13
Q
Alternation of generations
A
- Alternation of generations is found in many multicellular protists, all land plants and some fungi.
- Both the haploid and diploid forms are multicellular.
- The diploid form gives rise to spores and the haploid form gives rise to gametes.
14
Q
Sexual reproduction in fungi
A
Different groups of fungi reproduce in different ways.
Most spend the majority of their time in the haploid state.
Three stages in sexual reproduction:
• Plasmogamy(fusion of cytoplasm)
• Karyogamy (fusion of nuclei)
• Meiosis
15
Q
Reproduction in angiosperms
A
- Sperm from stamen must reach ovules in order for reproduction to occur
- this take place via Abiotic (enviromental) or Biotic (oragnism) factor
16
Q
External fertilization
A
• Aquatic only • Useful for sessile organisms • Requires behaviours/ adaptions to ensure gametes meet • Often limited control over whose gamete fertilises egg
17
Q
Internal fertilization
A
• Terrestrial and aquatic • Generally motile because need to find a partner • Can be selective over who fertilises egg • Many behaviours/ adaptations to choose partner and compete with rivals
18
Q
Oviparous
A
Egg laying • Embryos develop externally • Nutrients for development are in the egg • Shell protects embryo and impedes water loss
19
Q
Viviparous
A
• Live young • Embryos develop internally • Nutrients from mother • Mother’s body protect embryo
20
Q
Why does life respire?
A
• Respiration is the process by which an organism exchanges gases between
themselves and the environment.
• All species (unicellular and multicellular) respire to release energy from their food
to fuel cellular processes.
• Different organisms have different structures and mechanisms to respire.
21
Q
What are different type of respiration?
A
Organisms can extract energy from food via:
1) Aerobic cellular respiration: organisms use oxygen to extract energy from food.
2) Anaerobic cellular respiration: organisms do not use oxygen to extract energy from food but
instead use a different compound (e.g. nitrate or sulfur).
3) Fermentation: The anaerobic degradation of a substance such as glucose to smaller molecules
such as lactic acid or alcohol with the extraction of energy.
Note: fermentation does not use the electron transport chain so is not considered respiration.
22
Q
Benefits of aerobic and anaerobic respiration
A
Aerobic respiration • Releases more ATP molecules than anaerobic respiration • This may have allowed for the evolution of multicellularity and larger organism size Anaerobic respiration • Quickly releases energy • Can occur in low oxygen environments
23
Q
Where did mitochondria come from?
A
Mitochondria evolved via endosymbiosis where a host cell engulfed an
prokaryote cell.
There are two hypotheses regarding the types of organisms involved:
1) The traditional view is that a eukaryote host engulfed an aerobic
prokaryote.
2) An alternate view is that a prokaryote host engulfed a facultative
anaerobic prokaryote.
This is part of the endosymbiotic theory
24
Q
Bacteria and Archaea respiration
A
Bacteria and archaea can respire aerobically, anaerobically or both.
Respiration occurs in the cytoplasm of the cell.
1. Obligate aerobic bacteria cannot survive without oxygen.
2. Obligate anaerobic bacteria cannot survive in the presence of
oxygen.
3. Facultative anaerobic bacteria can grow without oxygen but use
oxygen if it is present.
Anaerobic bacteria use other compounds such as hydrogen sulfide or
methane, instead of using oxygen.
25
Aerobic respiration in fungi
Most fungi are aerobic, but some are anaerobic.
In soil, hyphae absorb oxygen from tiny air spaces in between soil
particles.
Oxygen and carbon dioxide can move across the thin outer wall of
hyphae by absorption
26
Fermentation and food
We rely on fungi for bread, miso, olives, beer and wine.
We use bacteria for cheese, olives, soy sauce, yoghurt, kimchi,
kombucha and more.
This is called fermentation and involves using bacteria or yeast to break
down starch and sugar
27
Respiration in plants
All parts of a plant need to respire. Plants obtain oxygen via diffusion through:
1. stomata (leaves and stems)
2. lenticels (stems of woody plants and some roots)
Plants also obtain oxygen via absorption through roots
-rate of respiration is relate to sunlight intensity
28
Specialise Respiration adaptation in plant roots
Roots have adaptations depending on the oxygen environment.
Aerial roots known as pneumatophores are useful in environments
with anoxic or waterlogged soil.
Aerenchyma are small air pockets in plant tissue. Allows for exchange
of gases from exposed parts of the plant to submerged parts.
29
Respiration in plant leaves
-Leaves and some stems have stomata which are tiny openings that
allow for gas exchange.
-Stomata a present in the sporophyte generation of all land
plants (except liverworts).
-Stomata can open and close, depending on plant condition and
environmental condition.
30
Respiration in animals
```
Different animals have different systems to supply oxygen to
cells and remove carbon dioxide waste.
Five different types of gas exchange systems in animals are:
1) Direct diffusion
2) Integumentary exchange
3) Trachea
4) Gills
5) Lungs
There are four possible stages of respiration in animals, but not
all animals use all four:
1) Breathing
2) Gas exchange
3) Circulation
4) Cellular respiration
```
31
Direct diffusion
Small animals (<1mm diameter) can obtain oxygen via
diffusion.
Direct diffusion of oxygen across the outer membrane can
supply oxygen to all cells.
Larger animals cannot use this method because diffusion
would not be able to provide oxygen quickly enough.
32
Integumentary exchange
Some animals, such as earthworms and amphibians, use their
skin as the gas exchange surface.
Gases diffuse directly across the integument (i.e. skin) into the
circulatory system
33
Trachea
Insects have a system of tubes branching throughout their body to provide oxygen to all cells. These tubes are called trachea.
The openings to trachea are called spiracles and these can be opened or closed when needed.
Some insects can ventilate the tracheal system with muscle contractions.
The tracheal system is separate to the circulatory system.
34
Gills
Gills are found in molluscs, annelids, crustaceans and fish.
Gills can be found in a cavity or externally on different species.
Gills are highly branched and folded thin tissue filaments. Water passes over the gills and oxygen rapidly diffuses across the gills into the circulatory system or coelomic fluid.
Many gills use a counter current system to gain oxygen and lose carbon dioxide
35
Lungs
Lungs are found in amphibians, birds, reptiles and
mammals.
Lungs vary greatly across the animal kingdom:
• Amphibians have a simple sac like lung.
• Reptile lungs vary but tend to be sac like,
sometimes subdivided.
• Mammals have branching lungs that terminate in
tiny air filled sacs (alveoli).
• Bird lungs are composed of a parallel series of
tubes, the parabronchi.
36
Weird respiratory systems
Some animals breathe through their butt:
• Sea cucumbers have specialized respiratory trees
in just inside their anus.
• Fitzroy river turtles can obtain up to 70% of its
oxygen needs through its cloaca. This is termed
cloacal gill respiration.
The diving bell spider can hold onto an air bubble as
they dive underwater.
37
How did respiration evolve?
- After the great oxygenation event around 3.5 B years ago
| - sharply increase one million years ago
38
How does oxygen level influence evolution?
-giant insect
39
Why does life on earth require food?
• All individuals, regardless of whether they are a single-celled or multi-cellular organism, require
food (a resource) to maintain normal cellular function and replication, and, to reproduce.
• The required food is either consumed directly or synthesised by the individual.
• One way to classify organisms is based on how they acquire their food.
40
Autotrophs
```
• Autotrophs (auto = self; trophe =
nutrition)
• Are represented in all three Domains
and four of the six Kingdoms of life
(Bacteria, Archaea, Protista, Plantae)
• Synthesise the food they require for
life (but may need to source other
nutrients such as Nitrogen, N, from the
environment).
```
41
Heterotrophs
• Heterotrophs (heteros = other; trophe =
nutrition)
• are unable to make their own food, and
so must consume other sources
of organic carbon and other nutrients
(i.e. by consuming other forms of life).
• are found in all Domains and Kingdoms
of life, and is the exclusive mode of
feeding for the Kingdoms Fungi and
Animalia.
42
Autotrophs – Types and Importance
Autotrophs can be divided into two broad groups:
1. Chemoautotrophs – these are bacteria that also synthesise their own organic
molecules using the oxidation of inorganic compounds (hydrogen gas, hydrogen
sulfide, methane, or ferrous ions) as a source of energy, rather than sunlight.
2. Photoautotrophs – these green plants, some bacteria and algae manufacture
all their required organic molecules from simple inorganic molecules, using
sunlight as the energy source for photosynthesis.
43
Heterotrophs – Types and Importance
Heterotrophs can be divided into multiple groups depending on what
they eat:
1. Carnivores - eat animals
2. Insectivores - eat insects
3. Herbivores - eat plants
4. Omnivores - eats meat, plants, fungi etc.
5. Scavengers - eat remains of food left by carnivores and herbivores
6. Detritivores - eat soil, leaf litter and other decaying organic matter
44
Heterotrophs – The ancestral state
• Earliest life forms were likely single-celled primitive heterotrophs that would have resembled modern day bacteria
• Fed by absorbing acid and base molecules in the early organic (C) oceans
• This chemical breakdown was a form of fermentation
• We use similar fermentation methods when making beer, cheese and
sour dough bread
45
Photoautotrophs – A chance event that changed the planet
* The earliest photoautotrophs were likely photosynthetic bacteria
* These early forms were capable of anoxygenic photosynthesis – a photosynthetic pathway that occurs in the absence of oxygen and does not generate oxygen
* Increased levels of oxygen favoured oxygenic photosynthesis – photosynthetic pathway that both requires and generates oxygen
* Oxygenic photosynthesis evolved about 2.7 billion years ago in bacteria that were similar to modern cyanobacteria
* Then…. early eukaryotic cells engulfed photosynthetic bacteria (through endocytosis) resulting in the first plant cells – endosymbiotic theory
46
The endosymbiotic theory – how multiple cells became one
* Originally called symbiogenesis (sym = together, bios = life, genesis = origin).
* Proposed for the evolution of eukaryotes from prokaryotes over 100 years ago but needed electronmicroscopes to prove (achieved in the 1960’s)
* Mitochondria and Chloroplasts are well known endosymbionts (referred to as organelles)
47
The endosymbiotic theory – Empirical support
• Phylogenetically related: Chloroplasts (related to cyanobacteria) and
mitochondria (related to proteobacteria)
• Genome reduced: As organelles, Mitochondria and Chloroplasts have their
own DNA but the genome size is reduced compared to their prokaryote
ancestors
• Across species the number of chloroplasts can vary; in some species of algae
there is only one per cell, but a typical leaf the size of your hand can contain
between 3 and 5 billion!
48
Autotrophs – chemoautotrophs
• Chemoautotrophs can use inorganic compounds (hydrogen sulphide, sulphur,
iron) or organic sources if available.
• Likely that these species formed some of the earliest biological communities. • Majority live in hostile environments (such as deep sea vents or volcanic springs)
where photo-autotrophs would not survive.
• They are critically important primary producers in these ecosystems.
49
Autotrophs – photoautotrophs (anoxygenic)
Anoxygenic photoautotrophs use H2S or organic molecules as a source of electrons
• They have bacteriochorophylls rather than chloroplasts
• Many of species adapted to live in harsh conditions such as in hot springs, and
stagnant water
• Important for nutrient recycling in their environments
50
Autotrophs – photoautotrophs (oxygenic)
These species use the oxygen from water in photosynthesis and produce oxygen as
a biproduct
Cyanobacteria (Domain: Bacteria)
• Earliest oxygenic photoautotrophs (single-celled cyanobacteria)
• Additional nutrients are obtained via diffusion or osmosis from the water
Algae (Domain: Eukaryote)
• Include the closest relatives of land plants (green algae)
• Multicellular and larger in size (although typically thin – increased SA:Vol)
• Require water - moves passively across their cell walls, provides nutrients. • No water-absorbing or water-conducting structures and desiccation not an issue
51
Autotroph adaptations: the challenges of living on land
• On land, water and other nutrients are limited and often in the soil
• Plants (Domain Eukaryote, Kingdom Plantae) have evolved many adaptations to
enable them to obtain the resources they require
Adaptations to living on land:
• Roots to extract water and dissolved nutrients from soil
• Vascular tissue for transporting water and nutrients
• Water-resistant coating (cuticle) to minimise water loss to the atmosphere
• Tissue for structural support
• Diversity of leaf types and size for photosynthesis
52
Autotroph adaptations: the importance of roots
• The earliest vascular land plants did not have true roots – see Fork Fern (top right)
Roots:
• Are the underground organs of vascular plants
• Support nutrient (e.g. N, P, K and Ca, Mg, S) and water uptake from the soil
• Provide anchorage and support (important as plants increase in size)
• Synthesis of plant hormones and storage of nutritional reserves
• Can be modified (aerial roots for O2 uptake in salt marshes and swamps; clasping
roots in climbing plants; prop roots that support and contractile roots to pull the
plant firmly into its substrate).
53
Autotroph adaptations: the vascular system
• The vascular system consists of phloem for the transport of sugars and xylem for
the transport of water and mineral ions
• In more advanced vascular plants the xylem is reinforced by a rigid layer of lignin
• Trees, have long stems and produce large amounts of wood through secondary
growth
Two reasons the vascular system allowed for increased size:
• The conducting system allows transport of sugars and water to larger areas
• Lignin prevents xylem cells from collapsing under hydrostatic pressure.
54
Autotroph adaptations: the importance of leaves
• Land plants originally had their photosynthetic apparatus on the stems
• Leaves evolved multiple times in land plants and provided an increased SA for
photosynthesis and gas exchange
• Leaves are thought to have evolved from modified branches that overlapped and
flattened
• Leaves are the most important organs of most vascular plants
• The structure and diversity of leaves is enormous and varies depending on the
type of environment and ecological niche
55
Autotrophs: Ingenious adaptations to get food
Parasitic plants (e.g. mistletoe) • Derive all of their nutrients from other plants
• Have modified roots that penetrates the host plants walls connecting them to the vascular
system (either the xylem, phloem or both)
Carnivorous plants (e.g. Venus flytrap) • Derives some nutrients from capturing prey (insects and arachnids) • Have a trapping structure typically triggered by tiny “trigger” hairs on their inner surfaces.
Symbiotic legumes (e.g. pea plants) • Many legumes house other symbiotic nitrogen-fixing bacteria (e.g. Rhizobium) in root
structures called root nodules
• These bacteria are beneficial when soils have poor nutrients (e.g. N)
Symbiotic autotrophic algae (e.g. zooxanthellae) • Zooxanthellae live in symbiosis within coral • They provide nutrients to coral (sugars, glycerol, amino acids) and gain CO2
, phosphates, and
nitrogen compounds in return
56
Heterotroph feeding strategies: Diffusion and Phagocytosis
• Diffusion - movement of nutrients through the cell membrane (Domain/Kingdom: Bacteria) • Phagocytosis - engulfing items of food or prey (Kingdom Protista: Amoeba, Kingdom Animalia: Sponges)
- Evolved specialised structures or cells to assist
57
Heterotroph feeding strategies: Filter Feeding
• Filter feeders feed by straining organic matter and food particles from water, typically by passing
the water over a specialized filtering structure
• An incredible diversity of species that have evolved this mode of feeding.
58
Heterotroph feeding strategies: external digestion
Fungi (Kingdom: Fungi) • Feed by absorption of nutrients from the environment
• Hyphae (filamentous structure of fungi) grow through the substrates
• Hyphae secrete digestive enzymes which break down the substrate, making it easier for
the fungus to absorb the nutrients which the substrate contains.
Insect species (Kingdom: Animalia; Phylum: Arthropoda - houseflies) • First tastes the food with its feet • Has sponge-like mouthparts that can suck up liquid, but they are unable to chew larger
sources of food
• excretes enzymes to digest the food
59
Heterotrophs: diversity of mouthparts - invertebrates
• Invertebrates have evolved perhaps the greatest diversity of mouthparts
• Insects typically spend a disproportionate amount of their lives as juveniles where they accumulate the
resources necessary for producing offspring as adults
• The mouthparts and feeding strategies of the adult and juvenile stages of an insect can be very different • Some insects do not feed at all as adults
60
Heterotrophs: the evolution of jaws - vertebrates
• Earliest fish were jawless – lamprey and hagfish
• Jaws were derived from gill arches
• Once jaws evolved, teeth soon followed
• The evolution of jawed fish is linked to declines of marine
invertebrates such as trilobites
61
Heterotrophs: evolution of teeth - vertebrates
```
Homodonts
• All teeth are the same shape
• Typical of non-mammalian vertebrates including sharks and
reptiles
Heterodonts
• Have a variety of tooth shapes
• Typical for mammals
• Most mammals have incisors, canines, premolars, and molars
Teeth further modified depending on ecology
• Predators
• Herbivores
• Bark scraping
```
62
Definitions: excretion and secretion
• Excretion is the removal of ‘waste’ products by an organism
• Excretion regulates the internal environment in three main ways:
(i) controls cell/body water content
(ii) maintenance of solute composition, and
(iii) excretion of metabolic waste products and other unwanted
substances
• Excretory products can be liquids, gases or solids
Contrast with
• Secretion is the movement of material that has a specific task after leaving
the cell or organism
63
Definitions: elimination and respiration
• Elimination ‐ the removal of unabsorbed food that has never been part of the
body, typically in the form of faeces.
Contrast with
• Respiration ‐ the process by which an organism exchanges gases between
themselves and the environment.
64
Why is excretion and elimination important?
• An inability to remove excretory or waste products can lead to disruption
of cell membranes, inefficient metabolism and may lead to death
• All species across all kingdoms have evolved means by which to effectively
excrete and eliminate waste
• These processes vary with across the kingdoms but also depend on the
ecological niche of the species
65
Excretion and elimination can be passive
In principle, all the transport systems described for gaining resources function in
the opposite direction and thus can play a role in the excretion of certain
metabolites.
Passive transport
• where solutes cross the membrane without the involvement of a specific
transport protein.
• movement of solutes (proteins, amino acids or other biproducts) occurs due to
the chemical gradient of the solute and thus through osmosis and diffusion.
• Common in bacteria, fungi and to some degree aquatic plants
66
Excretion and elimination is mostly active
• In principle, all the transport systems described for gaining resources function in the opposite direction and thus can play a role in the excretion of certain metabolites.
Active transport
• Most species have specialized cells or organs that have evolved to assist with excretion and elimination.
• Active transport of waste products allows for organisms to be larger and more complex in size.
67
Specialised cells that assist with excretion: plants
• Guard cells are located on the outer surface of leaves and stems
• They are produced in pairs with a gap between them (stomatal pore)
• They are involved in gas exchange and assist with controlling water loss
• The stomatal pores open most when the plant has lots of water and the
guard cells are swollen
• The stomatal pores close when water availability is low and the guard cells
shrink.
68
Specialised cells that assist with excretion: animals
Flame cells ‐ specialized excretory cells found in freshwater invertebrates (e.g. rotifers, flatworms)
• Flame cells function like the mammalian kidney – they remove waste materials
• Bundles of flame cells are called protonephridia
69
Specialised organs in animals that assist with excretion
Animals have evolved a range of organs that assist
specifically with excretion
• Early animals (aquatic flatworms) have protonephridia
• Later animals (annelids and arthropods) have evolved
more complex nephridia, along with associated glands
• Vertebrates have kidneys and a liver (along with
associated glands)
70
: the importance of the coelom
coelom absent = “ACOELOMATE”
coelom present = “COELOMATE”
• Fluid‐filled so can be used as internal support
• Separates internal processes from gut
• Allows transport of fluids (circulatory and excretory systems)
• Provides space for development of internal organs
• Enables increased body size
71
Excretion in protists and early eukaryotes
• Single‐celled organisms have just the one cell to play with and there are
no specialised organs.
• The majority of waste and biproducts of metabolism are eliminated by
passive diffusion and osmosis.
• Active transport of waste (chemicals) occurs through specialised
membrane channels and/or are expelled directly.
72
Excretion in Fungi
• Fungi also have no specialised organs to excrete waste
• Some waste and biproducts of metabolism are eliminated by passive
diffusion and osmosis.
• Active transport of waste (chemicals) occurs through specialised membrane
channels and/or are expelled directly using a comparable method to bacteria
(exocytosis with food vacuoles – or contractile vacuoles)
73
A tale of fungal serendipity that revolutionized medicine
• On 3 September 1928, Fleming returned from his holiday to
discover he had left inoculated staphylococci (bacteria) on culture
plates on a bench in a corner of his laboratory.
• The plates were contaminated with a fungus, and colonies of
staphylococci immediately surrounding the fungus were
destroyed, whereas other staphylococci colonies farther away
were normal.
• He identified the mould as being from the genus Penicillin and
realized that it produced an antibiotic now known as penicillin
• Estimated that penicillin has saved between 80‐200 million lives
74
Excretion in plants: three key mechanisms
1. Transpiration: Gaseous wastes and water are excreted through
stomata, lenticels of the stem, and the outer surface of the stem or
fruits
2. Storing: Some organic waste is stored in plant parts such as barks and
leaves
3. Diffusion: Aquatic plants excrete metabolic wastes through diffusion.
Terrestrial plants excrete into the soil.
75
Excretion in plants: transpiration
• Water is necessary for plants but only 0.5‐3% taken up by the roots is used
for growth and metabolism.
• The remaining 97–99.5% is lost by transpiration and guttation
• Transpiration occurs during the day when the stoma are open
Guttation
• drops of xylem (carries water) sap gather on the tips or edges of leaves of
some plants and a number of fungi
• Guttation usually happens at night when the stoma are closed and water
builds up due to root pressure
• It is not the same as dew, which is condensed water from the atmosphere
76
Excretion in plants: storage of waste
• Plants produce waste materials that get accumulated in the vacuoles of
ageing cells
• These storage structures can be stems, leaves or bark of trees
• These cells eventually die and fall‐off‐the plant
• Excretion is important as it rids potentially toxic substances
• It can be manipulated by humans – rubber and maple syrup
77
Excretion in plants: diffusion
* Water (and soil nutrients) diffuses into plants through their root hair cells.
* Water moves from an area of high concentration (in the soil) to an area of lower concentration (in the root hair cell). This is because root hair cells are partially permeable. The diffusion of water like this, is called osmosis.
* Diffusion of nutrients no longer required by the plants can also occur through the roots in terrestrial plants
* In aquatic plants diffusion through leaves and the roots is an important pathway to expel nutrients
* Root hairs increase the surface area for water and nutrient uptake and excretion facilitating this process
78
Nitrogenous waste: a common problem
* Protein is ubiquitously required by heterotrophic animals and metabolism of protein leads to high concentrations of nitrogen waste.
* The form of the nitrogen waste varies for different animals,depending on their environment and phylogeny.
* The organs that animals have evolved to process N also varies from simply cell like structures in flatworms to the complex kidneyin vertebrates
* Animals convert excess N into Ammonia, urea, uric acid and guanine
* Most aquatic species excrete ammonia
* Most terrestrial species convert the N to urea or uric acid
* Spiders excrete guanine
79
Advantages and disadvantages of different N products
• Ammonia (one N per molecule) - requires lots of water for excretion and is very
toxic. However, it is extremely soluble and no energy is expended in its
synthesis.
• Urea (two N per molecule) - less toxic and requires less water for excretion, but
its synthesis is more complex and has a metabolic cost of four ATP molecules
per molecule of urea.
• Uric acid (four N per molecule) - highly insoluble and non-toxic, so its excretion
conserves water, but its synthesis is more complex and entails a higher
metabolic cost of 24 ATP molecules per molecule of uric acid.
• Guanine (five N per molecule), is also nearly insoluble and can be excreted with
little water loss, but it comes at a high energy cost
80
Excretory organs in animals: invertebrates
* Excretory organs in invertebrates (including annelids or insects) transport waste from the coelom to the exterior.
* The excretory organs increase in complexity from simple protonephridia (found in marine worms) the more complex nephridia (earthworms and some insects) and the Malpighian tubule system (found in many insects and spiders).
* In insects (and birds and reptiles), the hindgut is involved in both excretion and elimination; N waste first moves into it prior to excretion (usually mixed with faeces)
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Excretory organs in animals: kidneys and the liver
1. The Kidneys – These are the primary excretory organ of vertebrates although various other organs, including the skin, gills and gut assist with solute and
water regulation
2. The Liver ‐ is an important organ of excretion in vertebrates. It breaks down many substances in the blood, including toxins, and assists with the
breakdown of red blood cells.
In birds and reptiles, excretion and elimination of waste occurs
from the hindgut via a single opening (the cloaca); mammals have a separate opening for each.
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Movement: the process of moving from one place to another
Why do individuals move?
• find food
• a mate
• suitable habitat to live • escape predators.
In this lecture we will consider: • Movement of individuals; and briefly, • The means by which species that do not move ensure their offspring do
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Passive movement: advantages and disadvantages
Advantage of passive movement - involves little or no energy expenditure
• Organisms can move passively largely through water and air, however, • Some species attach themselves to ‘hosts’ (e.g. parasites, spores or
seeds)
Disadvantage of passive movement – you have little or no control over where
you end up
• Possible you move to an environment that is suboptimal for your own
development • Some species employ both passive and active movement
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Active movement: advantages and disadvantages
Advantage of active movement – more control of where they move to
• Organisms actively move through all environments
Disadvantage of active movement – energy is required for movement • Individuals must balance investment in resources for movement against
those they can invest in cellular maintenance and reproduction
• Some species employ both passive and active movement
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Moving in water
Living in water provides several advantages for species
• Support – no accident that the blue whale lives in the water
• Hydration – desiccation not a problem
• Nutrient rich
• Environmentally buffered
Movement in water is challenging
• Strong currents – you can end up in a suboptimal environment • Buoyancy – maintaining position requires energy and/or specialized
structures
• Water levels might fluctuate (evolution of land species)
Species have evolved a range of structures to facilitate active movement in water • Cilia & flagella
• Feet-like projections/structures
• Fins and flippers (birds and mammals)
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Moving on land
Living on land presents many challenges
• Oxygen in air – need to evolve means to capture
• Lack of water – dehydration and dessication is a major problem
• UV radiation – causes DNA and cell damage
• No support – species require structures that support them
• Energy hungry – passive movement is typically limited
• Terrestrial ecosystems are complex and vary dramatically
Species have evolved a range of structures to facilitate active movement on land
• Cell walls
• Vascular tissues
• Lignin and bark
• Seeds or spores
• Legs
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Moving in the air
Air is possibly the safest but most challenging environments to move in:
• Gravity wins – adaptations required to ensure lift
• Strong wind currents – can end up in suboptimal environment
• Extremely energy hungry – flying takes enormous muscles
Adaptations required to take to the air:
• Light – taken by the wind anyway
• Produce lots of seeds - chance of landing in good environment is low
• Large surface area for lift – helicopter seeds, wings, gliding membranes
• Enlarged muscles for flight – may need to trade off against something else
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Early adaptations that facilitate active movement
Three main adaptations in prokaryotes and eukaryote protists
1. Cilia – tiny hairs that cover the outside of the cell
2. Pseudopods (False feet) – move out in specific directions
3. Flagella – longer hair like structure that is propelled around
(rather like a helicopter blade)
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Early adaptations: cilia
• Unicellular species that use cilia tend to be:
- larger than species that use a flagellum
- move faster than species that use a flagellum
• Marine annelids and most molluscs (including slugs and snails) have a larval phase that uses cilia to move through the water
• Cilia beat in a co-ordinated movement across the cell
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Early adaptations: Pseudopods (false-feet)
• Unicellular amoebae alter their cell shape by pushing cytoplasm outwards to
produce pseudopodia (false feet).
• They can have multiple pseudopodia projecting from the cell in different
directions but can also use this to move in a particular direction.
• When food is in scare supply, individual amoeba can aggregate to form a
single travelling colony (either as multiple cells or congregating to form a
single massive cell.
Comparable structure in animals: Some animal species (marine worms) have parapodia
(leg-like structures) – these are paired appendages which are based on a comparable
design to pseudopods (ie fluid filled and assist in movement) but they have nervous
control
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Early adaptations: flagella (flagellum – singular)
Evolved as a whip like appendage that protrudes from the cell body of prokaryote and eukaryote bacteria
• Its primary function is locomotion
• Locomotion is often along a single plane
• Can also function as a sensory organelle
Comparable structure in animals: larvae of sponges have a flagellum that assists with movement. The majority of sperm in animals has a flagellum that is critical for sperm motility
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A Nobel prize-winning flagellum: Serendipity strikes again
• Suspected of causing gastritis and stomach ulcers for over 100+ yr • 1970s - Marshall and Warren were still unable to culture
• In 1982, they returned after a five week Easter break to discover that
petri dishes they’d left inoculated contained the bacteria
• The scientific community remained skeptical and so, • Marshall drank a beaker of H. pylori culture ***
• He became extremely ill with gastritis
• H. pylori was found to be the causal agent
• They subsequently demonstrated that antibiotics could cure it
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Cnidarians: active propulsion
Adult Jellyfish (free-swimming form of Cnidarians) • Move through the water by expanding and contracting their bell-shaped
bodies to push water behind them
• Muscles assist in this process
• This is an incredibly energy efficient means of moving in water
• The congregate in large masses or blooms to obtain good nutrients and prey
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Molluscs: active propulsion
Squid, octopus, cuttlefish, Nautilus (Cephalopods - marine Molluscs)
• Take in water through their mouths and then contract their body to push the
water through their funnel thus achieving forward propulsion.
• Muscles assist in this process
• Their tentacles can also aid in movement: control of direction and can act as
pseudo-legs when not swimming (they can also assist when walking on land
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Molluscs: movement on water and land
Molluscs have variations on a similar body plan:
• Mantle - dorsal (back) body wall which in some species forms a shell
• Muscular foot - used for moving, feeding, manipulation
• Not all species move as adults (although they do all have trochophore larvae)
Movement
• Cephalopods use propulsion (see previous slide) • Slugs and snails move by rhythmic waves of muscular contraction on the underside of its foot.
• They secrete mucus to assist with movement • The mucus is particularly helpful on land
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Annelids: adapted for movement in water and on land
Marine worms
• Free-swimming & sedentary
• Have unjointed leg-like ‘parapodia’ on every body segment
• Trocophore larvae - free swimming ciliated larva
Earthworms
• Mostly terrestrial - live in soil (feed on organic matter) • Can grow very long – Gipsland earthworm up to 3m
• React to vibrations
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Vertebrates: evolved in the water and moved onto land
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Vertebrates are a subphylum of Chordates
All chordates have a:
• Notochord
• Dorsal nerve chord
• Myomeres (segmented muscles)
Early chordates including fish have: • Gill slits
• Post-anal tail (aids movement)
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Cartilaginous v bony fish: movement and buoyancy
• The earliest fish had a cartilaginous skeleton (Sharks and Rays)
• The bony skeleton evolved later (all other fish and all vertebrates)
• Fish move using their caudal tail and fins (fins vary across species)
• Movement is active and assisted by muscle
• Maintenance of buoyancy – essential to save energy
Cartilaginous fish
• Large liver (25-30% of body weight) filled with low-density oil (still need to
swim to maintain buoyancy
• Cartilage which is lighter than bone
• Pectoral fins provide dynamic lift
Bony fish
• Have a swim bladder for buoyancy
• Swim bladders are evolutionarily closely related (i.e., homologous) to lungs
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The evolution of sturdier fins: the precursor to legs
Most bony fishes have fins made of long rays of bone (ray-finned fishes)
• Some fishes developed more substantial bones in the fins (lobe-finned fishes) e.g. lungfish
• These bones would have been able to support the weight of the fish
• 350 Mya some lobe-finned fish, living in shallow lagoons, evolved bones that allowed them to ‘walk’ (paddle in shallow water)
• These early amphibians had both gills and lungs (c.f. lungfish – some use their their swim bladder as a lung when on land)
Amphibians today still require water to reproduce
• Tadpoles (aquatic) have gills
• Adult frogs (terrestrial) have lungs
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Insects: the first colonisers of the skies
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Insects (Kingdom: Animalia, Phylum: Arthropoda, Class: Insecta) •
Hard exoskeleton (cuticle)
• Moult
• Inhabit water, land and air
• Six legs
• Wings
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Evolution of insect flight
Wing - stiff membrane of exoskeleton strengthened by “veins”
• Most likely evolved from gills in aquatic forms • Traditionally thought wings evolved from structures that would help ‘gliding’ • Evidence from stoneflies suggests early wings aid locomotion across water surface
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The archosaurs: the relationship between reptiles and birds
• Reptiles are adapted to survive to reproduce without water
• Belong to the archosaurs (along with dinosaurs and pterosaurs).
However:
• The archosaurs is not a monophyletic group
• Strictly speaking should include the birds
• Birds evolved from dromaeosaurs
• In 1861, in Germany, a new fossil was discovered that had dromaeosaur
characteristics but also…
• Feathers and wings – evidence for evolutionary origin of birds from dinosaurs
Adaptations for flight • Bones less dense
• Enlarged chest muscle for flight • Feathers
• System of air sacs in their body that connect to the lungs – allows them to
extract much more oxygen per breath
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The evolution of mammals and a change of stance
• Mammals also evolved from reptiles and walk upright
• Hip joints, and upper limb bones changed in mammals and dinosaurs
• Changed stance
• Change of stance enabled quicker locomotion (longer
legs)
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A legacy of change of stance
• Fish move their bodies from side to side when they swim
• Sprawling animals like crocodiles and lizards do the same
• Change of stance: mammals move the back half of body forward and back (bend in different
plane)
`• Dolphins and whales swim the same way (compare with fish)
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From quadraped to biped: the human story
• Humans walk upright habitually (bipedal)
• Great apes typically ‘knuckle walk’ (quadruped)
Changes in skeletal structure
• Big toe reduced
• Pelvis shortened, more bowl-like than blade-like (helps support base of spine)
• Femur bends inwards, knee straightened, patella central
to joint
• Connection with spinal column (foramen magnum) on underside of skull
• Less robust upper arms
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The human advantage
* Upright walking freed hands for other purposes
* Humans have greater manual dexterity
* Greater tool use
* Ability to throw accurately (important in hunting)
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The fossil record is incomplete
Fossils are the preserved remains or any preserved trace of a once living organism.
Any living thing can become a fossil, but most organisms do not fossilize. Organisms are more likely
to fossilize if:
• They have bones or hard structures.
• The organism is quickly covered after it dies. For example, by seafloor sediment, lava or tar.
• The remains are in an anoxic environment.
• The chemistry of the environment doesn’t dissolve the organism.
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How do we date fossils?
Relative dating:
• Stratigraphy can be used to order layers of rock from older to more recent, at a single location.
• Index fossils are fossils with a known date, and can be used to date other unknown fossils if found together.
Absolute dating:
• Radiometric dating methods based on the decay of certain
elements (e.g. carbon) can be used to date fossils.
• Different elements are used depending on the timescale.
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What can fossils tell us?
* Dates
* Physiology
* Diet
* Reproductive mode
* Movement
* Migration
* Development
* Thermoregulation
* Colour
* Behaviour
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What are major evolutionary transitions?
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Major evolutionary transitions “involved changes in the way information is stored and transmitted”
Major evolutionary transitions involve:
• New units of reproduction
• Division of labour/cooperation
• Development of more complex units
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Major evolutionary transition - Multicellularity
Multicellularity has evolved multiple times.
Organisms alive today can help us to understand the evolution of multicellularity.
Fossils can help us to understand when multicellularity evolved.
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Evolutionary events – Dawn of animals
Fossil evidence suggests the first animal was similar to a sponge.
Biomarkers suggest support the fossil evidence and suggest that animals had evolved by about 635 mya.
Around 575 mya, larger and more diverse animals appear – the Ediacaran fauna (named after a place in Australia).
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Origination and extinction of species
Throughout the history of life, new species evolve (origination) and other species die out (extinction).
The rate of origination and rate of extinction can be used to understand diversity and identify adaptive radiations and mass extinctions.
The fossil record helps to determine the rate of origination and rate of extinction.
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What is an adaptive radiation?
Adaptive radiations are when evolutionary lineages undergo exceptionally rapid diversification into a variety of lifestyles or ecological niches.
Occur more often on islands or in lake systems.
Most adaptive radiations involve exploitation of a new environmental niche in the absence of competition
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What is a mass extinction
Extinctions can occur from many causes, including a change in the climate, habitat loss, competition or predation.
A mass extinction is a statistically significant departure from background extinction rates that results in a substantial loss of diversity.
Mass extinctions can be local or global, taxonomically specific or taxonomically broad, and can occur over different time scales.
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“The Big Five
1) Ordovician
2) Devonian
3) Permian
4) Triassic
5) Cretaceous
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End-Ordovician mass extinction
Ended 443 mya and was caused by an increase in extinction rates.
Within 3.5 to 1.9 million years, 50-60% of marine genera and nearly 85% of marine
species were lost.
The increase in extinction rates was caused by climate change.
1) First there was global cooling and glaciation, causing sea level fall, loss of shallow
water habitat and change in ocean chemistry.
2) Then there was global warming, causing sea level rise and change in ocean chemistry.
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End-Triassic mass extinction
Ended 200 mya and was caused by an increase in extinction rates and reduction in origination rates.
Within 2.8 to 0.2 million years, 47% of genera and 80% of species were lost.
The increase in extinction rates was caused by increase in volcanic activity, thought to have increased atmospheric CO2. This led to increased temperatures and a calcification crisis in the oceans.
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The Anthropocene
There are many organisms that have gone extinct
due to humans.
The dodo
• Explorers to Mauritius in the 1600s killed the
dodo for sport.
• They also introduced rats that ate dodo eggs.
The Tasmanian tiger
• Declared extinct in 1936.
• Settlers hunted the Tasmanian tiger, destroyed
its habitat and introduced disease
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Are we heading to a sixth mass extinction?
- Rate of extintion are rising and are similar to when the big 5 occur
- the current rates is faster than extimated speed
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Human causes of extinction
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There are many human actions that can lead to
extinction of a species. These include:
• Habitat loss
• Species introductions
• Pollution
• Overexploitation
• Climate change
Extinction of one or a few species can have
cascading effects.
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Habitat loss
Habitat loss can occur for many reasons including deforestation, agriculture, or urban
development.
Many types of habitat are affected, from forests to wetlands.
Case study: Hawai’i
• 1/3 of endangered birds are in Hawai’i.
• 113 birds are only found in Hawaii, 71 have
become extinct and 31 more are threatened.
• One cause is wetland loss.
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The oceans are becoming more acidic
Carbon dioxide dissolves in the ocean, reacts with water and produces carbonic acid.
Ocean pH has dropped by from 8.21 to 8.10 since the Industrial Revolution. This affects calcifying marine life.
