Reproduction and Growth

Reproduction and Growth

Middle School

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Learning Objectives

• Explain how different animal behaviors contribute to reproductive success.

• Analyze how genes and the environment interact to influence the growth and traits of plants.

• Use Punnett squares to predict the outcomes of simple genetic crosses and differentiate between inherited and acquired traits.

• Compare and contrast the reproductive structures and life cycles of major plant groups.

Key Vocabulary

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Courtship

The ritual behaviors that mates use to recognize, attract, and accept one another for mating.

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Pheromone

A chemical signal released by an animal that affects the behavior of others of its species.

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Mating System

The specific pattern of mate relationships within a species, such as monogamy or polygyny.

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Gene

A distinct section of DNA that holds the specific instructions for building a particular protein or trait.

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Allele

One of the different versions or forms of a particular gene that can exist.

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Genotype

An organism's specific combination of alleles, often represented by letters like TT, Tt, or tt.

Key Vocabulary

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Phenotype

An organism's observable traits, which come from its genes and the surrounding environment.

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Punnett Square

A chart used to predict the possible genetic outcomes of offspring from a specific cross.

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Sporophyte

The stage in a plant's life cycle that produces spores through a process called meiosis.

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Gametophyte

The stage in a plant's life cycle that produces gametes, which are the sperm and egg.

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Finding and Choosing a Mate

Mate Choice

• One sex, usually the female, chooses a mate based on specific qualities or behaviors.

• These can include bright colors, vigorous songs, or building elaborate structures like nests.

• This choice helps ensure that offspring will have strong and healthy genes.

Competition

• Members of the same sex, often males, will fight for the right to mate.

• Competition can involve direct physical contests, like two deer wrestling with their antlers.

• Establishing dominance or guarding a mate are other forms of competition.

Multiple Choice

What is the main purpose of mate selection behaviors like choosing a mate with bright colors or competing with others?

• To ensure that offspring will have strong and healthy genes

• To establish a social hierarchy within a group

• To find new sources of food and water

• To defend a territory from predators

Multiple Choice

How does mate competition differ from mate choice?

• Competition involves contests within the same sex, while choice involves one sex selecting a mate.

• Competition is only for territory, while choice is only for nesting sites.

• Competition involves songs and dances, while choice involves physical fights.

• Competition occurs among females, while choice is made by males.

Multiple Choice

In a species of bird, males with the brightest feathers are more likely to reproduce. Which statement provides the best explanation for this situation?

• She is using his bright colors as a sign that he has strong and healthy genes to pass on.

• She is helping him practice for a physical contest against other males.

• She is choosing the male that is best at finding food for the family.

• She is trying to distract him so another male can build a better nest.

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Parental Care

Altricial Young

• Altricial young are born helpless, often with their eyes closed and without feathers.

• They depend entirely on their parents for food, warmth, and protection from predators.

• These young must stay in a nest or den for an extended period.

Precocial Young

• Precocial young are born in an advanced state and are mobile shortly after birth.

• They can often walk, swim, or run and can find their own food.

• Parental care is focused on guidance and protection rather than constant feeding in a nest.

Multiple Choice

What is the main difference between altricial and precocial young?

• Their level of development and independence at birth.

• The number of offspring produced in a litter.

• The climate in which the species lives.

• The size of the parents.

Multiple Choice

Why do the parents of altricial young need to provide constant care in a nest or den?

• They are born helpless and cannot get their own food.

• They are born in an advanced state and can run immediately.

• They can find their own food shortly after birth.

• They have feathers and can keep themselves warm.

Multiple Choice

A young animal is able to walk and find its own food shortly after being born. What can be concluded about the type of parental care it will most likely receive?

• The young will need to be fed by its parents in a den.

• The young will be helpless and unable to move for weeks.

• Parental care will focus on guidance and protection.

• The parents will need to bring it food constantly.

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Inherited Traits and Basic Genetics

Types of Traits

• A trait is any observable feature, such as your natural eye color or a flower's color.

• Inherited traits are passed from parents to their children through genes.

• Acquired traits are developed from the environment, such as a scar from an injury.

Genotype & Phenotype

• A gene is a stretch of DNA with instructions for a trait, like flower color.

• Genotype is the allele combination (e.g., Pp), while phenotype is the resulting observable trait.

• An organism can be homozygous (PP or pp) or heterozygous (Pp) for that trait.

Multiple Choice

Which statement best defines an inherited trait?

• A feature passed from parents to their children through genes.

• A feature developed from the environment, such as a scar.

• The specific combination of alleles for a gene, such as Pp.

• A stretch of DNA with instructions for a specific feature.

Multiple Choice

What is the relationship between an organism's genotype and its phenotype?

• An organism's genotype determines its observable phenotype.

• An organism's phenotype determines its genetic genotype.

• The genotype is an acquired trait, while the phenotype is an inherited trait.

• The genotype and phenotype are different terms for the same feature.

Multiple Choice

A plant has a genotype of 'Pp' for the trait of flower color. Based on this information, what can be concluded about the plant?

• The plant is heterozygous for the flower color trait.

• The plant's phenotype for flower color is 'Pp'.

• The plant is homozygous for the flower color trait.

• The plant's flower color is an acquired trait.

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Dominant, Recessive, and Punnett Squares

• A dominant allele (P) shows its effect with just one copy present.

• A recessive allele (p) only shows its effect when two copies are present.

• A Punnett square is a tool to predict allele combinations in offspring.

• A Pp x Pp cross results in a 1 PP : 2 Pp : 1 pp genotype ratio.

Multiple Choice

Under which condition does a recessive allele show its effect?

• When at least one copy of the allele is present

• When two copies of the allele are present

• When it is paired with a dominant allele

• Only when the organism is a parent

Multiple Choice

What is the primary function of a Punnett square?

• To determine the exact traits of a single offspring

• To show which parent has dominant alleles

• To predict the potential allele combinations in offspring

• To count the number of genes in a chromosome

Multiple Choice

In a cross between two parents with the genotype Pp, what is the probability that an offspring will have the same genotype as the parents?

• 25%

• 50%

• 75%

• 100%

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Factors Influencing Plant Growth

• A plant's growth depends on both its genes and its environment.

• ​Genetic factors set the instructions for a plant's potential characteristics.

• Environmental factors include light, water, temperature, and soil nutrients.

• Growth is controlled by the scarcest resource, like a nutrient deficiency.

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Multiple Choice

What are the two primary types of factors that determine a plant's growth?

• Genetic and environmental factors

• The amount of sunlight and water available

• The plant's height and the color of its leaves

• The type of soil and the current season

Multiple Choice

What is the primary role of genetic factors in a plant's development?

• They provide the instructions for the plant's potential traits.

• They control the amount of water available to the plant.

• They determine the temperature of the surrounding air.

• They ensure the soil has enough nutrients for growth.

Multiple Choice

A plant has genes for growing tall and is in a warm environment with plenty of sunlight, but is planted in soil that lacks nutrients. What is the most likely outcome for this plant?

• Its growth will be limited by the lack of soil nutrients.

• It will grow tall because of its genetic instructions.

• It will grow tall because it has enough light and warmth.

• It will change its genes to adapt to the poor soil.

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Reproductive Structures: Seed Plants

Angiosperms

• ​The main reproductive organ is the flower, which uses features like petals to attract animal pollinators.

• ​​Flowers contain the stamen, which produces pollen, and the carpel, which contains the ovules for reproduction.

• ​After fertilization, the ovule develops into a seed and the ovary grows into a protective fruit.

Conifers

• ​The main reproductive organs are cones, which come in two different forms on the same plant.

• ​​They have small pollen cones to make pollen and larger seed cones that hold the ovules.

• ​After wind pollination, the ovule becomes a ‘naked’ seed that is not enclosed within a fruit.

Multiple Choice

What is the primary role of flowers and cones in seed plants?

• To produce food through photosynthesis

• To anchor the plant in the ground

• To facilitate the plant's reproduction

• To absorb water and nutrients from the soil

Multiple Choice

What is a key difference between how angiosperms and conifers reproduce?

• Angiosperms use cones and wind, while conifers use flowers and animals.

• Angiosperms use flowers to attract pollinators, while conifers rely on wind.

• Angiosperms produce 'naked' seeds, while conifers protect seeds in fruit.

• Angiosperms have carpels with ovules, while conifers have only pollen cones.

Multiple Choice

A scientist discovers a new plant species whose seeds are not enclosed in a fruit. Which of the following is most likely also true about this plant?

• It has large, colorful petals to attract animals.

• It relies on the wind to carry its pollen.

• Its ovules develop inside a protective fruit after fertilization.

• Its main reproductive parts are the stamen and carpel.

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Reproduction in Spore Plants

Moss Life Cycle

• Mosses reproduce using spores and require water for the sperm to swim to the egg.

• The visible green part of a moss is the gametophyte, the dominant stage of its life.

• A stalk-like sporophyte grows from it and releases spores from a capsule into the air.

Fern Life Cycle

• Ferns also use spores for reproduction and need water for fertilization to take place.

• The visible plant with leafy fronds is the sporophyte, the dominant stage of its life.

• Spores are produced in structures called sori on the underside of the plant's fronds.

Multiple Choice

What is the primary way that both mosses and ferns reproduce?

• By releasing spores into the air and water

• By attracting insects with colorful flowers

• By developing seeds within a protective cone

• By sending out roots to create new plants

Multiple Choice

What is a key difference between the life cycle of a moss and the life cycle of a fern?

• The visible moss is the gametophyte, while the visible fern is the sporophyte.

• Mosses release spores from sori, while ferns release them from a capsule.

• The moss is a leafy frond, while the fern is a small green stalk.

• Mosses require water to reproduce, while ferns do not.

Multiple Choice

If a moss and a fern were growing in an area that experienced a severe and prolonged drought, what would be the most likely impact on their ability to reproduce?

• Fertilization would fail because the sperm could not reach the egg.

• The spores would be unable to be released from the sori and capsules.

• The gametophyte and sporophyte stages would switch their dominant roles.

• The plants would immediately wilt and die from dehydration.

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Common Misconceptions

Misconception	Correction
A dominant trait is always better or more common.	Dominance is about how a trait is expressed, not how common it is.
Traits acquired during life, like big muscles, are passed to offspring.	Only inherited traits in your DNA can be passed to your children.
All plants reproduce using seeds from flowers.	Some plants use cones, and others like mosses and ferns use spores.

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Summary

• Animal behaviors like communication and competition are key to successful reproduction.

• An organism's traits result from its genes and its environment.

• Sexual reproduction creates genetic variation, which can be predicted using Punnett squares.

• Plants reproduce in diverse ways, such as with spores, cones, or flowers.

Poll

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