1. SEXUAL AND ASEXUAL 2. LIFE CYCLES OF PLANTS AND INSECTS 3. FLOWERS AS REPRODUCTIVE STRUCTURES 4....
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Transcript of 1. SEXUAL AND ASEXUAL 2. LIFE CYCLES OF PLANTS AND INSECTS 3. FLOWERS AS REPRODUCTIVE STRUCTURES 4....
1. SEXUAL AND ASEXUAL2. LIFE CYCLES OF PLANTS AND INSECTS3. FLOWERS AS REPRODUCTIVE STRUCTURES4. REPRODUCTIVE STRATEGIES IN ANIMALS
Definition of asexual reproduction:
• No fertilisation• Only one parent• No genetic variation
as opposed to ...Lorraine Kuun, July 2011
Fertilization Two parents Genetic variation
Gametes fuse to form zygote, containing genes from both parents.
Further variation brought about by:1.Crossing over during meiosis, prophase I2.Random assortment and segregation of
chromosomes3.Random fertilisation4.Mutations
Lorraine Kuun, July 2011
1.Binary fission – “splitting in two” – mitosis, e.g. bacterium: Escherichia coli
Lorraine Kuun, July 2011
2. Budding – new individual develops as outgrowth on parent organisms e.g. Yeast cells.
Lorraine Kuun, July 2011
3. Spore production – spores produced during favourable conditions e.g. Fungi
Lorraine Kuun, July 2011
4.Vegetative reproduction – vegetative part of plant, i.e. root, stem of leaf develops into new plant; can be natural or artificial.
Lorraine Kuun, July 2011
Buds on leaf margins e.g. Kalanchoe
Bulbs
Tubers
Lorraine Kuun, July 2011
DISADVANTAGES OF ASEXUAL REPRODUCTION
1.No genetic variation – adaptation may be difficult
2.All share same “weak characteristics” – may die out when environmental conditions change/become unfavourable
3.Mass reproduction can threaten environment – carrying capacity
Lorraine Kuun, July 2011
ADVANTAGES OF SEXUAL REPRODUCTION
1.Genetic variation2.Possible better
adaptations to changing environment
3.Role in natural selection
4.Better chances of survival
Lorraine Kuun, July 2011
DISADVANTAGES OF SEXUAL REPRODUCTION
DISADVANTAGES OF SEXUAL REPRODUCTION
1.High energy cost – gametes to be produced, gestation, parental care etc.
2.Needs two parents3.Slower, longer process4.Young can be vulnerable to
predators5.Extended periods of parental
care6.Plants may need pollinatorsLorraine Kuun, July 2011
1. Gametophyte: generation producing gametes in gametangium/ gametangia sexual stage.
2. Sporophyte: generation producing spores in sporangium/ sporangia – asexual stage.
NB: In higher plants the generations alternate in the life cycle of a plant; in lower plants reproduction is either through gametes (sexual) or spores etc. (asexual).
1. A haploid gametophyte generation that produces gametes (n) by mitosis ...
the gametes (n) fuse toform zygote (2n), the start of ...
2. A diploid sporophyte generation that
produces spores (n) by meiosis.
Leaf-like structures of moss gametophyte
Sporangium of moss sporophyte
INSECT METAMORPHOSIS
Physical changes from one stage in life cycle to another.
TWO TYPES OF METAMORPHOSIS:
1. Complete metamorphosis
2. Incomplete metamorphosis
88 % of all insects 12 % of insects
COMPLETE Four stages: 1. egg 2. larva 3. pupa 4. adult
E.g. Butterflies, bees, housefly
INCOMPLETE Three stages: 1. egg 2. nymph 3. adult
E.g. Locust, cricket, cockroach
Advantages:1.Vulnerable pupa
stage avoided.2.Less energy is
needed – no drastic changes from pupa to adult.
3.All stages can eat same food.
Disadvantages:1.Nymph and adult often
compete for same food.2.Insect vulnerable to
dehydration and predators when moulting.
3.Entire insect population could be threatened by environmental changes.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
1. Male (no pistil) or female (no anthers) flowers on different plants – dioecious.
2. Protandry – pollen ripe before stigma is receptive.
3. Protogyny – stigma receptive, but pollen not ripe yet.
i.e. self-pollination is prevented.
Lorraine Kuun, July 2011
Most pollinators are insects e.g. Bees, moths, butterflies, beetles.
Some vertebrates also pollinate flowers e.g. Bats, mice, birds (mainly).
Many flowers are pollinated by wind.
Lorraine Kuun, July 2011
Bright colours (bees cannot see red), white for night pollinators e.g. moths
Often sweet scent (attracts moths and butterflies)
Reward of nectar and pollen Contrasting markings on petals to locate
centre of flower (usually not visible to human eye – ultraviolet)
Pollen cling to hair on insect bodies
Lorraine Kuun, July 2011
High yield of dilute nectar Bigger than most insect-pollinated flowers Open in daytime, often red Sturdy against rough feeding of birds Little or no scent – birds have poor sense of
smell Protect ovary against beaks by being
inferior or by partition Pollen sticks together in clumps Often erect or with landing platform for
birds that do not hover
Lorraine Kuun, July 2011
Flowers do not have scent, nectar or brightly coloured petals – no need to attract pollinators.
Flowers high on plant to be exposed to wind. Flowers usually small and reduced, lacking
calyx or corolla (sepals and petals). Anthers large and well-exposed. Masses of light, non-sticky pollen produced. Stigmas long and feathery with large area
for trapping pollen.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
The fruit develops from the following layers:
• Fruit wall from ovary wall.
• Seed from ovule.
Lorraine Kuun, July 2011
A seed consists of a
1. Seed coat – outer layer of ovule (pericarp).
2. Embryo – from fertilisized egg cell (zygote undergoes mitosis).
Lorraine Kuun, July 2011
Endosperm – result of double fertilization. Endosperm is food for embryo – also why we eat seeds for food.
Lorraine Kuun, July 2011
Resistant to unfavourable conditions as they have seed coat.
Can be dispersed effectively (see later). Can remain viable in dormant state for long
periods. Seeds have stored food reserve in
endosperm or cotyledons; includes starch, oils and or protein.
Important to man as they are cheap form of plant propagation, way to store plants and are a store of food.
Lorraine Kuun, July 2011
Dormancy is a state of rest. Embryo inactive, seed will not germinate.
Some plants have obligatory period of dormancy – seed will not germinate even if conditions are favourable.
Dormancy prevents seeds from hatching in wrong season when seedlings would be exposed to unfavourable conditions. Allows seeds to survive unfavourable conditions.
Allows for seed dispersal agents to act.
Lorraine Kuun, July 2011
Wind – seeds are light with plumes or wings.
Animals – hooks and thorns – cling to wool, stick in paws.
Humans – edible fruit – seeds egested in different position.
Water – seeds contain oil or air bubbles – float away.
Self-dispersed – fruit dry, dehiscent.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
COCO DE MER drifts along ocean currents
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Most important plant source of food for humans.
Practical form of food – easy to transport and store for long periods of time.
Grains – wheat, maize (mealies), sorghum, rice, oats; mainly starch
Pulses (legumes) – beans, peas, soy beans, peanuts, lentils, plant proteins
Nuts – oily seeds in hard shells e.g. walnuts, cashews, pecans etc.
Lorraine Kuun, July 2011
Many plant species under threat. Seed bank stores seeds of wild plants and crops. UK – conserves seeds of about 10% of wild plant
species at Kew – Millennium Seed Bank Project. Swedish International Seed Vault – reinforced
concrete tunnel – 4,5 million seed samples – will remain viable for 1000’s of years.
MSBP working with SA National Biodiversity Institute – contributing 2500 indigenous species – endangered, endemic, over-exploited
Lorraine Kuun, July 2011
Can be used to 1. re-establish damaged, lost habitats and
ecosystems2. re-introduce extinct, endangered or
threatened species3. provide research material
Lorraine Kuun, July 2011
THANK YOU
THE ULTIMATE GOAL OF EACH SPECIES
Lorraine Kuun, July 2011
To produce the maximum number of surviving offspring ...
while using the least amount of energy.
This is called the reproductive effort.
Lorraine Kuun, July 2011
1. Courtship2. External vs Internal fertilisation3. Ovipary, ovovivipary and
vivipary4. Precocial and Altricial
development5. Amniotic egg6. Parental care
Lorraine Kuun, July 2011
Simple strategies include pheromones (chemical), brightly coloured body parts (visual) and mating calls (auditory) stimuli.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Complex strategies, unique to species, include courtship displays, annual rut (period of sexual excitement), lek breeding system, courtship-feeding.
Lorraine Kuun, July 2011
Courtship display strategies unique to each species; can include movement, calls, seasonal colour patterns etc.
Lorraine Kuun, July 2011
Bluecrane male trying to attract female’s attention by an elaborate dance
1. Females will be in peak condition to nurture developing baby.
2. Young are born when enough food is available to enable them to reach reproductive age.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Above: male springbok displayLeft: male cichlids make bowersfor females to lay eggs
Lorraine Kuun, July 2011
Male hoopoe feeds female; if she accepts, they will mate
Males and females find suitable mates e.g. male with best genetic potential.
Sexual behaviour in courtship is timed so that male and female both ready for mating at same time.
Energy expenditure by male; female conserves energy for breeding.
Lorraine Kuun, July 2011
Disadvantages of external fertilisation (outside the body):
1.Wasteful; huge loss of energy – many eggs produced, few survive.
2.Fertilisation not certain.3.Environmental conditions important for hatching of eggs
Lorraine Kuun, July 2011
1. Huge numbers of eggs increases probability of fertilisation.
2. Courtship rituals ensure that males and females are closer to each other.
3. Eggs of marine species release species-specific chemotactic factor to attract sperm.
4. Spawning is timed to occur when ocean currents can disperse eggs e.g. sessile species.
5. Young easily dispersed by sea currents; reduce competition.
6. No complicated physical mating, using energy.7. Larval form gets food directly from
environment; no energy input from parent.Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Mating occurs, but no copulation
Occurs in insects and terrestrial vertebrates i.e. birds, reptiles and mammals.
Marine mammals and some fish e.g. sharks and rays also have internal fertilisation.
Mating and copulation occurs. Most animals have cloaca – common opening
for reproduction and egestion – during fertilisation cloacas are lined up.
Male insects and mammals have a penis – organ to transfer sperm to body of female.
Fluid inside female provide medium for sperm to swim towards egg cell(s).
Lorraine Kuun, July 2011
1. Fertilisation is more certain – gametes placed closer together. Fewer gametes needed.
2. Energy saved in producing fewer gametes can be used for other purposes.
Lorraine Kuun, July 2011
1. Yolk to feed young.2. Shells that enclose eggs (oviparity); better
protection increases survival rate.3. Some fertilised eggs very well-protected
e.g. Sharks (ovoviviparity) and mammals (placenta).
4. Less wastage of gametes – in humans one egg per month produced.
There is a disadvantage: a cooperative partner is needed!
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
OVIPARY – eggs are released and develop outside body of female, fertilisation internal or external, egg yolk only nutrition.
OVOVIVIPARY – Internal fertilisation, egg shell soft, eggs hatch inside body, appears to be born alive, egg yolk nutrition, mother for protection.
VIVIPARY – fertilisation internal, no egg shell, nutrition via placenta.
Lorraine Kuun, July 2011
Most fish, amphibians and lower aquatic forms.
Needs large numbers of eggs.Larval stage self-sufficient; don’t compete with parents – use different food sources.
Eggs and larvae easily dispersed.
Lorraine Kuun, July 2011
Invertebrates produce large numbers of eggs to ensure survival (no or little parental care).
Protective shell prevents embryo from drying out.
Fewer eggs in e.g. birds and reptiles – energy can be used for more food in egg (yolk and albumin), hatching and protection, parental care.
Development of amnion important factor in success.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Hard shell good protection for developing embryo; prevents embryo from drying out.
Lorraine Kuun, July 2011
Shark egg pouch with yolk clearly visible
1. Fewer eggs needed – higher survival rate of offspring.
2. Developing embryo much less vulnerable to predators.
3. Developing embryo not subject to environmental changes e.g. temperature.
4. Young born fully developed, can feed and escape predators more easily.
5. Occurs in some invertebrates, fish and reptiles.
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Young puff adder being “born alive” after hatching inside mother; note position of cloaca.
Occurs in placental mammals, some sharks and scorpions
Fertilisation internal, no shell Placenta responsible for nutrition – young
born alive
1. fewer eggs necessary 2. energy available for nourishment and
protection of embryo, as well as parental care
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Ground-nesting birds e.g. Penguins, domestic poultry, ostriches
Large mammals e.g. Elephants, species of antelope, horses etc
Allows young to fend for itself, feed and stay warm
Stay with herd for protection against predators
Learn from older individuals in herds OFFSPRING HAS GOOD CHANCE OF SURVIVAL
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Left: Penguin chick andAbove: foal, both mobile soon after birth
Small animals that produce big litters e.g. mice, rats, cats, dogs
Tree-nesting birds that have nests away from predation
Humans (see human reproduction) Altricial species need parental care for a
long time – usually female that does the caring, male sometimes involved.
Birds usually have mouth-lining or gape-edge
Mammals small and immature brains
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Altricial bird – see mouth-lining that attracts mother
Lorraine Kuun, July 2011
Mice survive in broods, cared for by mother (left);Kittens born weak and totally dependent on mother (below)
Adaptation of later vertebrates; can lay eggs in terrestrial environment.
Amniotic egg has fluid-filled, extra-embryonic membranes that prevents embryo from drying out.
Earlier vertebrates lay eggs in water; need to return to water/live in water to reproduce.
Amniotic egg lessens dependence on water for reproduction.
Lorraine Kuun, July 2011
Fertilisation is internal. Extra-embryonic (not part of embryo)
membranes only develop after fertilisation. Membranes are:1. Amnion2. Allantois3. Yolk sac4. Chorion
Major evolutionary development; allowed first reptiles to colonise land!
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
The fluid-filled amnion surrounds and protects the embryo, especially against dehydration and shock.
Allantois acts as reservoir for nitrogenous waste in birds and reptiles.
Yolk sac holds nutritious food for development of embryo.
Chorion surrounds all other membranes: in birds it allows for gaseous exchange; in mammals it forms the placenta (taking over functions of allantois and yolk sac, amongst others (see human reproduction).
Lorraine Kuun, July 2011
Lorraine Kuun, July 2011
Any pattern of behaviour in which parent spends time or energy to improve the 1survival, 2condition and 3future reproductive success of offspring.
Care can be given at any stage:1.Prenatal – guarding eggs, building nests,
carrying broods, incubating eggs and placental nourishing.
2.Post-natal – providing food, protecting offspring, teaching offspring.
Lorraine Kuun, July 2011
Little or no parental care means a low reproductive effort.
Reproductive energy put into producing masses of eggs.
High mortality rate amongst eggs as well as young.
Few individuals survive to reproductive age. E.g. Most fish, amphibians, insects, most
reptiles
Lorraine Kuun, July 2011
Few eggs or young produced. Low mortality rate amongst eggs or young. High reproductive effort. Reproductive energy goes into parental
care after birth (post-natal). Most offspring survive to reproductive age. E.g. Mammals, birds, some reptiles,
exceptions amongst fish and Arthropods.
Lorraine Kuun, July 2011
Left: Midwife toad
Right: chicken laying egg, mother feeding young
Lorraine Kuun, July 2011
Ovovivipary type of parental care
Left: Male seahorse with young emerging from breeding pouch
Lorraine Kuun, July 2011