Animal Biology Part 1 & 2

Topic 4: Circulation Respiration Topic 5: Reproduction Topic 6: Nervous, Sensory, Motor systems

Sexual vs Asexual Reproduction

Sexual reproduction involves two diploid parents producing a haploid gamete through mitotic cell division. (sperm and eggs) genetic diversity in the population. Offspring inherit a mmix of genes.

Asexual reproduction do not require a partner, instead by themselves. Well suited to stable/non-changing environments.

Disadvantages of asexual reproduction

Limited genetic diversity (all offspring and similar)

Can accumulate harmful mutations over generations (muellers ratchet)

Populations are more vulnerable to environmental changes overtime.

Disadvantages of sexual reproduction

Uses more costs and energy

Requires finding another mate

Can break up locally- adapted genes can reduce fitness in stables environments.

Isogamy

All gametes are the same size

iso=same

No differentiated sexes, any gametes can fuse with one another

Anisogamy

Gametes are all different sizes

High investment—>large, few eggs, produced by mostly females. (sessile)

Low investment—> small, many sperm, produced by many males. (Mobile)

Disruptive selection favours small or large gametes.

Can lead to sex specific behaviours e.g. ornamentation

Fertilisation strategies

Uniting male and female gametes (formation of a zygote can occur)

Maximise reproduction + fertilisation

Offspring size is influenced by internal/external fertilisation and environment.

Internal Fertilisation

Land common

Sperm (sessile) delivered near to the female reproductive tract.

Reaching female part prevents drying out

Targeted nature (fewer gametes are produced)

Copulatory orans—>gamete transfer mechanisms

External fertilisation

Common in water

Gametes released to their surroundings

Synchronised reproduction of gametes to increase chances of fertilisation.

Hydra reproductive systems

Sexual and asexual reproduction

Budding—>small clones from parent detaches and grows into a new individual

sexually—> through combining gametes to create genetically different/diverse offspring.

Parthenogenesis

Eggs develop into offspring without fertilisation e.g. lizards

Offspring genetically identical to the mother.

Advantageous in stable environments.

Hermaphroditism

E.G. earthworms

Individuals have both male and female reproductive parts.

Either self-fertilisation or to find a mate

Increase reproductive flexibility.

Sequential Hermaphroditism

E.g. fish like the Blue Groper and Barramundi

Can change their sex during their lifetime

Occurs in response to population pressures

E.g. shortage of females or males.

What are the development strategies?

Ovoparity

Ovoviviparity

Viviparity

Ovoparity—>development strategies

Egg laying

Young hatch outside of the mother (embryo obtains energy from the egg yolk.)

E.g. most arthropods, many fish, amphibians, most reptiles, monotremes and birds.

Ovoviviparity—>development strategies

Embryo develops inside of the egg (Contains food from the yolk)

Hatches inside the mother

Young are born alive

E.g. some fish, many reptiles,

Convergent evolution from oviparous ancestor

Viviparity—>development strategies

Young development within the uterus.

Obtain food via the placenta

E.g. some sharks, some reptiles, mammals

Convergent evolution from oviparous ancestor.

Homeostasis

Body maintains a stable internal environment

Negative feedback counteracts changes and keeps conditions steady

Labour is special (uses positive feedback)

Homeostasis (Labour e.g. humans)

Positive feedback used

System amplifies change instead of opposing it

Estradiol increases oxytocin sensitivity

Oxytocin triggers uterine contractions, stimulating more oxytocin release

Loop continues until birth takes place.

Signals stop—>homeostasis is restored (controlled physiological process)

Nervous system consists of…

Nerve cells (neurons) and supporting cells (glia)

Every animals except sponges have a form of a nervous system

Animals differentiate based on neuron connection + organisation into circuits

x3 Nervous system functions:

Sensory input

Integration

Motor input

Sensory input—>Nervous system functions:

Receptors collect information about the surrounding environment

E.g. light collection detecting cells in an animals eye.

Integration—>Nervous system functions:

Sensory information is processed by interneurons in the central nervous system

This includes the brain and spinal chord.

Motor input—>Nervous system functions:

The central nervous system

Sends signals to affector cells (muscles or lands)

Sent through the peripheral nervous system to initiate a response.

Process mirrors components of homeostasis (1) detection, (2) Integration, (3) response.

Example: The Cone Snail

What are neurons:

Specialised cells

Cell body containing organelles

Dendrites—> receive signals,

Axons—> transmit signals

Neurons are connected via synapses and transmitted by them as well. (chemical or electrical transmissions)

Neuron Types: x3

Sensory Neurons

Interneurons

Motor Neurons

Sensory neurons—>Neuron Types

Found in peripheral nervous system, transmitting signals rapidly to the central nervous system.

Interneurons—>Neuron Types

Located in the central nervous system

Process information

Many connections to other neurons.

Motor Neurons—>Neuron Types

Signals are sent from the central nervous system to affector cells.

How do neurons work?