Evolution and life diversity Flashcards
Why reproduce?
-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.
different ways that organisms can reproduce
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.
Sexual reproduction evolution
- 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
Asexual reproduction
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
Sexual reproduction
Sexual reproduction is found only in the four Eukaryote Kingdoms of life (Protista,
Fungi, Plantae, Animalia).
Sexual reproduction differs greatly among species:
Asexual vs Sexual reproduction
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
Fission
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)
Budding
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.
Fragmentation
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.
Vegetative propagation
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
Spore formation
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
Parthenogenesis
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
Alternation of generations
- 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.
Sexual reproduction in fungi
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
Reproduction in angiosperms
- Sperm from stamen must reach ovules in order for reproduction to occur
- this take place via Abiotic (enviromental) or Biotic (oragnism) factor
External fertilization
• Aquatic only • Useful for sessile organisms • Requires behaviours/ adaptions to ensure gametes meet • Often limited control over whose gamete fertilises egg
Internal fertilization
• 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
Oviparous
Egg laying • Embryos develop externally • Nutrients for development are in the egg • Shell protects embryo and impedes water loss
Viviparous
• Live young • Embryos develop internally • Nutrients from mother • Mother’s body protect embryo
Why does life respire?
• 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.
What are different type of respiration?
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.
Benefits of aerobic and anaerobic respiration
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
Where did mitochondria come from?
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
Bacteria and Archaea respiration
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.
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
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
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
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.
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.
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
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.
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
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.
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
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.
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.
How did respiration evolve?
- After the great oxygenation event around 3.5 B years ago
- sharply increase one million years ago
How does oxygen level influence evolution?
-giant insect
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.
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).
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.
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.
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
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
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
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)
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!
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.
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
